(CNN) — The Biden administration said it has deployed federal medical experts to help assess what dangers remain at an Ohio village where a train carrying hazardous materials derailed this month, a ramp-up of federal support at the governor’s request as anxious residents point to signs of adverse effects.

Ohio Gov. Mike DeWine on Thursday asked the US Centers for Disease Control and Prevention and the US Department of Health and Human Services to send teams to East Palestine, where the train derailed February 3 and sparked a dayslong blaze.

“This request for medical experts includes, but is not limited to, physicians and behavioral health specialists,” DeWine wrote in a letter to the CDC. “Some community members have already seen physicians in the area but remain concerned about their condition and possible health effects — both short- and long-term.”

The Biden administration approved the request and began deploying teams from both federal agencies in part for public health testing and assessments, White House press secretary Karine Jean-Pierre said Thursday.

That is in addition to aid the Federal Emergency Management Agency is providing, according to Jean-Pierre, who noted Thursday that the train derailment situation is “much more expansive” than what FEMA can offer.

The federal support boost to a community of some 5,000 people along the Ohio-Pennsylvania state line comes amid some residents’ growing concerns that some areas may not be safe to live in.

An evacuation order that was in place for areas near the crash site was lifted February 8 after officials said air and water sample results led them to deem the area safe, officials said.

But a chemical stench lingered in areas, with some residents saying the odor left them with headaches and pains in their throat. Plus, officials estimate thousands of fish were killed by contamination washing down streams and rivers.

Further spurring residents’ questions about safety — some of which were expressed at an emotional community meeting Wednesday — were crews’ decision to conduct controlled detonations February 6 of some tanks carrying toxic chemicals to prevent a more dangerous explosion. Though a larger blast was averted, the detonations essentially released chemicals into the air, including vinyl chloride that at high levels could kill and increase cancer risk.

On Thursday, the head of the federal Environmental Agency Administration visited East Palestine and vowed to use the agency’s enforcement authority to hold the train operator, Norfolk Southern, accountable.

“I want the community to know that we hear you, we see you, and that we will get to the bottom of this,” EPA Administrator Michael S. Regan said Thursday during a news conference. “We are testing for all volatile organic chemicals. We’re testing for everything. We’re testing for everything that was on that train. So, we feel comfortable that we are casting a net wide enough to present a picture that will protect the community.”

During the visit, Regan observed some of the ongoing remediation efforts following the hazardous train derailment. While the state EPA has the primary responsibility over the scene, Regan noted the federal arm is ready to provide aid when needed.

Regan also noted that Norfolk Southern has signed a notice of accountability, acknowledging the company will be responsible for the cleanup.

Meanwhile, another train operated by Norfolk Southern derailed Thursday morning in Michigan’s Van Buren Charter Township, and local officials said there was no evidence the area was exposed to hazardous materials.

Where the investigation stands

Federal transportation investigators are working vigorously to determine what caused the 100-car freight train to crash in Ohio, the head of the National Transportation Safety Board said Thursday in a thread of tweets.

“You have my personal commitment that the NTSB will CONTINUE to share all information publicly as soon as possible following our analysis,” board chairwoman Jennifer Homendy wrote. “Next: NTSB investigators will thoroughly examine the tank cars once decontaminated. As always, we’ll issue urgent safety recommendations as needed.”

One of the elements under scrutiny is an apparent overheated wheel bearing seen on video before the derailment, the NTSB has said. The apparent overheating began at least 43 minutes before the train derailed, according to a CNN analysis of surveillance videos the network obtained.

At around 8:12 p.m. on February 3, sparks from an apparent wheel bearing overheating were visible as the train passed through Salem, Ohio, two surveillance videos obtained by CNN show. Bright light and sparks are seen emanating from one of the rail cars.

No sparks were seen in surveillance video taken 14 minutes earlier as the train passed through Alliance, Ohio.

The train derailed in East Palestine around 8:55 p.m., about 43 minutes after the sparks were seen in Salem.

It remains unclear what caused the overheating and whether it is linked to the derailment.

The train was carrying toxic materials including vinyl chloride, ethylene glycol monobutyl ether, ethylhexyl acrylate, isobutylene and butyl acrylate, the US Environmental Protection Agency has said.

Of those, the vinyl chloride gas that caught fire could break down into compounds including hydrogen chloride and phosgene, a chemical weapon used during World War I as a choking agent, according to the EPA and the CDC. Vinyl chloride — a volatile organic compound, or VOC, and the most toxic chemical involved in the derailment — is known to cause cancer, attacking the liver, and can also affect the brain, Maria Doa of the Environmental Defense Fund told CNN.

Resident worries not everyone is receiving proper testing

It’s the dangers these chemicals pose that has put East Palestine residents on edge over the past two weeks.

In a town hall meeting Wednesday, East Palestine Mayor Trent Conaway addressed the February 6 controlled detonations, saying the only option was to release the chemicals manually or risk greater danger to residents.

“There (were) two options: We either detonate those tanks, or they detonate themselves,” Conaway told a group of reporters at Wednesday’s meeting. “If we didn’t do that, then they were going to blow up, and we were going to have shrapnel all across this town.”

Jami Cozza, an East Palestine resident, said she will not return home until it’s safe. Cozza told CNN she’s staying at a hotel paid for by the train company due to toxicity in her home.

Cozza explained the train company told her it was safe to return home after conducting air testing. She insisted the company run soil and water tests, and only then did a toxicologist deem her house unsafe.

“Had I not used my voice, had I not thrown a fit, I would be sitting in that house right now, when they told me that it was safe,” Cozza said Thursday, adding she’s worried that not all residents are receiving the proper level of testing.

Cozza noted the company has also offered to pay all of her moving expenses. “It’s not about the money. It’s about our house,” she said.

Representatives of the train’s operator, Norfolk Southern, did not attend the community meeting Wednesday, citing safety concerns after it said employees were threatened, further escalating tensions.

Despite the company’s absence, the mayor said the operator has been collaborating with local officials “tremendously.”

Earlier this week, Norfolk Southern said it plans to create a $1 million charitable fund to support the East Palestine community.

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