Residents in and around East Palestine, Ohio, evacuated their homes in the aftermath of a massive train derailment, but the day after workers released chemicals from rail cars at risk of exploding they still do not know when they can go home.

Following a health warning and an evacuation order from Gov. Mike DeWine, crew members let vinyl chloride out of five cars, releasing it into a trough, and then burned it off while monitoring air quality. Fire and smoke filled the air during the process.

"Thus far, no concerning readings have been detected," Pennsylvania Gov. Josh Shapiro said at a news conference about three hours after the process started. East Palestine is located on the Ohio-Pennsylvania border.

Tuesday morning, DeWine told "Fox & Friends" that the situation was "so far, so good."

OFFICIALS ADVISE EVACUATION OVER EXPLOSION CONCERNS AFTER TRAIN DERAILMENT IN OHIO

Train derailment East Palestine, Ohio

A black plume rises over East Palestine, Ohio, as a result of a controlled detonation of a portion of the derailed Norfolk and Southern cargo on Monday, Feb. 6, 2023. (AP Photo/Gene J. Puskar)

Ohio National Guard members are expected to be going near the crash site wearing protective equipment, so they can check the air with sensors.

Authorities made one final pass to make sure residents were clear of the area before starting the release and burn of the chemical, although it was already believed most or all had followed instructions to evacuate.

"You need to leave, you just need to leave. This is a matter of life and death," DeWine declared at news conference.

NATIONAL GUARD CALLED IN TO ASSIST IN AFTERMATH OF OHIO TRAIN DERAILMENT

Ohio train derailment.

A train derailment in East Palestine, Ohio, caused a fiery wreck Friday. Crew members released and burned hazardous chemicals from five rail cars on Monday, after an evacuation order for nearby residents. (AP Photo/Gene J. Puskar)

East Palestine Mayor Trent Conaway declared a state of emergency for the village. He said one person had been arrested for going beyond barricades and approaching the crash site.

"I don’t know why anybody would want to be up there; you’re breathing toxic fumes if you’re that close," Conaway said.

Ohio train fire caused by derailment

Workers are still cleaning up the wreckage of the train derailment that took place in East Palestine, Ohio, on Friday, Feb. 3, 2023. (Melissa Smith via AP)

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Officials said the process would result in phosgene and hydrogen chloride being released into the air. Phosgene is highly toxic and can cause breathing difficulty and vomiting. According to the CDC, it was used in World War I and is currently used to make pesticides.

The wreck took place Friday night, when roughly 50 cars derailed, including 10 containing hazardous materials. According to federal investigators, the cause was a mechanical problem related to a rail car axle.

The Associated Press contributed to this report.