CNN– After federal officials released an initial report concluding that this month’s toxic train wreck in Ohio was completely preventable, investigators will begin examining procedures, practices and design prior to the derailment that has sparked long-term concerns among hundreds of frustrated residents.

The National Transportation Safety Board on Thursday released its preliminary report on the investigation into the February 3 train crash in East Palestine, Ohio, where residents have been complaining about feeling sick after hazardous chemicals seeped into the air, water and soil.

The report found that one of the train’s cars carrying plastic pellets was heated by a hot axle that sparked the initial fire, according to Jennifer Homendy, the chair of the safety board. As the temperature of the bearing got hotter, the train passed by two wayside defect detectors that did not trigger an audible alarm message because the heat threshold was not met at that point, Homendy explained. A third detector eventually picked up the high temperature, but it was already too late by then.

“This was 100% preventable. … There is no accident. Every single event that we investigate is preventable,” Homendy said during a news conference Thursday. “The NTSB has one goal, and that is safety and ensuring that this never happens again.”

The next phase of the investigation will examine the train’s wheelset and bearing as well as the damage from the derailment, the NTSB report noted. The agency will also focus on the designs of tank cars and railcars along with maintenance procedures and practices.

Plus, investigators will review the train operator’s use of wayside defect detectors and the company’s railcar inspection practices. More specifically, determining what caused the wheel bearing failure will be key to the investigation, Homendy said.

On Friday, Homendy said on “CNN This Morning” that she’s concerned politics could cloud the investigation and prevent safety improvements. Former President Donald Trump visited the site of the train derailment on Wednesday where he criticized President Joe Biden’s administration’s handling of the railway disaster.

“This is not a time for politics,” Homendy said. “There is a time for politics. It is not this.”

On Thursday, Transportation Secretary Pete Buttigieg also visited the derailment site, and when asked how political figures like Trump could help, Buttigieg addressed the former president directly saying he could “express support for reversing the deregulation that happened on his watch.”

Another key aspect of the investigation will focus on the response to the chemical disaster, particularly the manual detonations of tanks carrying toxic chemicals.

Five of the 38 derailed train cars were carrying more than 115,000 gallons of vinyl chloride, according to the NTSB’s report. Exposure to high levels of vinyl chloride can increase cancer risk or cause death.

Those five cars “continued to concern authorities because the temperature inside one tank car was still rising,” indicating a polymerization reaction which could have resulted in an explosion, the report said. To help prevent a potentially deadly blast of vinyl chloride, crews released the toxic chemical into a trench and burned it off on February 6 — three days after the derailment.

Since then, some East Palestine residents have said they are experiencing headaches, dizziness, nausea and bloody noses — a host of health issues they say they did not have prior to the crash.

At the same time, officials have been adamant in reassuring residents of the air’s safety and the municipal water supply.

Evidence does not show wrongdoing from crew

The 149-car train operated by Norfolk Southern on February 3 had three employees on board: a locomotive engineer, a conductor and a trainee who were all in the head end of the locomotive, Homendy told CNN’s Jake Tapper on Thursday.

So far, the investigation found the crew did not do anything wrong prior to the derailment, though the crash was “100% preventable,” Homendy said.

Video of the train before the derailment showed what appeared to be an overheated wheel bearing, according to the NTSB report. Footage showed sparks flying from underneath the train.

NTSB investigators are now focusing on one train car’s wheel set and bearing to figure out what may have caused the overheating, Homendy said.

“We have a lot of questions about that,” she said Friday, including the “thresholds and why they vary so much between railroads.”

Ultimately, it’s the railroads that set the temperature thresholds for the detectors, Homendy said.

Releasing publicly a probable cause or causes for the derailment could take 12 to 18 months, Homendy said during the news conference.

“We are very deliberative. We are the gold standard when it comes to investigations globally, and we are methodical in our approach,” Homendy said. “But if we see a safety issue that we need to be addressed immediately, something systemic, we will not hesitate to issue an urgent safety recommendation.”

In the meantime, here’s what the NTSB preliminary report found so far:

Even after reading the preliminary NTSB report, Ohio Attorney General Dave Yost told “CNN This Morning” that there’s still a lot of facts he doesn’t know.

Among his biggest questions are: “Had the train been shorter, had there been additional staff, could this have been averted? Based on the alerts that occurred, how long is the reaction time and how is that influenced by the size of the train?” Yost told CNN.

How officials have responded

The US Environmental Protection Agency has ordered Norfolk Southern to cover the full cost of cleaning up the aftermath of the train crash.

“EPA has special authority for situations just like this where we can compel companies who inflict trauma and cause environmental and health damage to communities, like Norfolk Southern has done, to completely clean up the mess that they’ve caused and pay for it,” EPA administrator Michael Regan said.

Norfolk Southern will be required to:

If the company does not follow the order, the EPA will step in to complete the duties, while fining Norfolk Southern up to $70,000 a day, Regan said Wednesday during a CNN town hall.

“And the law gives us the authority to charge Norfolk Southern up to three times the amount that the cleanup will cost us,” he said.

The company plans to take a series of measures moving forward to minimize the long-term impacts of chemicals on the land and groundwater, including ripping up the tracks where the train derailed and removing soil underneath, Norfolk Southern CEO Alan Shaw said.

Shaw added his company is working with the Environmental Protection Agency on a “long-term remediation plan.”

Expanding the definition of a high-hazard flammable train – a standard the derailed train did not meet, despite sparking a major fire – is among the changes NTSB advocated for in the past, Homendy said Friday.

NTSB urged regulators to include in the classification “a broad array of flammable materials,” rather than focusing on crude oil, she said.

Additionally, NTSB will look at whether vinyl chloride needs to be carried in more fortified cars, Homendy said.

Residents do not trust railroad company’s promises

During a CNN town hall on Wednesday night, some East Palestine residents directed questions to Norfolk Southern CEO Shaw and Ohio Gov. Mike DeWine.

The intense exchanges left residents frustrated as they said officials dodged their pressing questions, deepening their mistrust in the cleanup process.

Jim Stewart, a lifelong 65-year-old East Palestine resident who said he lives near where the crash happened, told Shaw he feels his health has been threatened by the derailment.

“Did you shorten my life now? I want to retire and enjoy it. How are we going to enjoy it? You burned me,” Stewart said, addressing Shaw. “You’ve made me an angry man.”

Other residents echoed Stewart’s sentiments — especially the safety concerns around their water supply and soil.

Nene Stewart, an East Palestine resident, told DeWine she has been relying on bottled water because she’s unsure whether her home’s water is safe.

“I’m not trusting what they are saying,” Nene Stewart said Wednesday evening. “So, I don’t know who is telling the truth.”

At the end of the town hall, Nene Stewart remained skeptical of the company’s promises on cleanup efforts.

Shaw declined on Wednesday to answer repeated questions from residents regarding the crash investigation and details about what could have caused the derailment, saying he was “prohibited” from talking about the probe.

“I’m terribly sorry that this has happened to this community,” he said. “What I can do, and what I will do, is make it right.”

“We’re going to get the cleanup right, we’re going to reimburse the citizens, we’re going to invest in the long-term health of this community,” Shaw said. “I’m going to see this through, and we’re going to be here. And we’re going to work with these community leaders to help you thrive.”

Norfolk Southern also plans to review the results of the National Transportation Safety Board’s investigation as well as use data to “figure out what we could’ve done better,” said Shaw, adding the company has already implemented new internal safety measures.

CNN’s Holly Yan, Christina Maxouris, Nicki Brown, Ross Levitt and Gregory Wallace contributed to this report.