Officials in northeastern Ohio are urging people who have not already evacuated the area to do so now after a train derailed in the state, leading to fears of a potential explosion.

Residents were warned of "the potential of a catastrophic tanker failure" after a "drastic temperature change" was discovered in the rail car, Ohio GOP Gov. Mike DeWine’s office said in a statement, adding that teams were working to prevent an explosion at the scene in the village of East Palestine.

Everyone within a 1-mile radius of the scene was advised to leave immediately. Many had already left the area, but local officials said more than 500 residents had opted to stay put as of Sunday night.

Federal investigators announced earlier on Sunday that a mechanical issue with a rail car axle caused the derailment Friday night near the Ohio-Pennsylvania border.

OHIO TRAIN DERAILMENT CAUSES MASSIVE FIRE, FORCES VILLAGE EVACUATION

Train derailment

This photo taken with a drone shows portions of a Norfolk and Southern freight train that derailed Friday night in East Palestine, Ohio.

National Transportation Safety Board member Michael Graham said at a news conference that the three-member train crew received an alert about the mechanical issue shortly before the derailment and that the board was still working to determine which rail car malfunctioned.

About 50 cars derailed in East Palestine as a train was carrying cargo from Madison, Illinois, to Conway, Pennsylvania, according to rail operator Norfolk Southern. No injuries were reported.

Graham said investigators located the exact "point of derailment." He said information will be included in a preliminary investigative report that will be released in the next month or so.

Local officials said emergency responders were monitoring the situation but keeping their distance from the fire, and that remediation efforts could not begin while the train cars were smoldering.

East Palestine Mayor Trent Conaway said one person was arrested for going around barricades and approaching the train. He warned of additional arrests if people did not stay away from the site.

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Train fire

A train fire is seen from a farm in East Palestine, Ohio.

"I don't know why anybody would want to be up there, you're breathing toxic fumes if you're that close," he said, emphasizing that monitors of air quality away from the fire did not show levels of concern and that the town's water is safe because it uses groundwater unaffected by some material that went into streams. 

Environmental protection agency crews were working to remove contaminants from streams and to monitor water quality.

Sheriffs knocked on doors in the area on Sunday to count residents remaining and encourage people within the evacuation area to leave. Schools and village offices will be closed at least through Monday. Businesses within the evacuation area are not permitted to open Monday.

Transportation company Norfolk Southern said 20 of the more than 100 cars on the train were classified as carrying hazardous materials. The company said only 10 cars carrying hazardous materials derailed, and five of them were carrying vinyl chloride. Officials said late Saturday that they had not confirmed the vinyl chloride had been released outside of pressure release devices operating as designed.

Vinyl chloride, used to make the polyvinyl chloride hard plastic resin in a number of plastic products, is associated with a heightened risk of some cancers, according to the federal government’s National Cancer Institute.

Fire from train derailment

A train derailment and resulting large fire prompted an evacuation order in the Ohio village near the Pennsylvania state line on Friday night.

"Short-term exposure to low levels of substances associated with the derailment does not present a long-term health risk to residents," according to a post on the village's Facebook page. "Vinyl chloride and benzene may cause cancer in people exposed in the workplace to high concentrations for many years; however, there is no indication that any potential exposure that occurred after the derailment increases the risk of cancer or any other long-term health effects in community members."

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Officials said Sunday afternoon that cars involved in the derailment also carried combustible liquids, butyl acrylate and residue of benzene from prior shipments. They also said nonhazardous materials such as wheat, plastic pellets, malt liquors and lube oil were being transported.

The evacuation order included 1,500 to 2,000 of the town’s 4,800 to 4,900 residents, although officials admitted it was unclear exactly how many were actually impacted. Most residents who had gone to an emergency shelter left by Sunday.

The Associated Press contributed to this report.