A drone footage shows the freight train derailment in East Palestine, Ohio
Drone footage shows the freight train derailment in East Palestine, Ohio, U.S., February 6, 2023 in this screengrab obtained from a handout video released by the NTSB. NTSBGov/Handout via REUTERS Reuters

Crews in eastern Ohio conducted operations on Monday to drain and burn off an "unstable" toxic chemical cargo from five rail cars of a freight train that derailed in a fiery wreck three days earlier, prompting mass evacuations, authorities said.

The "controlled release" of pressurized vinyl chloride, a highly flammable and carcinogenic gas, began with a scheduled explosion, followed by continuous burning of the substance, said Sandy Mackey, a spokesperson for the Ohio Emergency Management Agency.

"That controlled release was the one explosion," she told Reuters by telephone. "It went as planned. It seemed to be a successful incident."

No injuries were reported, Mackey added.

Live video footage shot by local media showed a towering column of thick, black smoke rising from the accident site in East Palestine, Ohio, a town close to the Pennsylvania border northwest of Pittsburgh.

The train, operated by Norfolk Southern Railroad, derailed late on Friday, setting off a massive fire that forced evacuation of homes in the immediate vicinity.

Public safety concerns deepened after the railroad said pressure-relief devices on some of the stricken cars were found on Sunday to have stopped working, which the company said could "result in a catastrophic failure."

Ohio Governor Mike DeWine said in a statement the chemical contents of the five rail cars in question were "unstable and could potentially explode, causing deadly disbursement of shrapnel and toxic fumes."

Working with state and local emergency officials, Norfolk Southern said on Monday it devised a plan to manually vent the cars, allowing the contents to "be drained in a controlled fashion" under supervision of "experts and first responders."

"This will be loud and visible," the company said, adding that "some of the material will burn off as it drains for a short number of hours."

As part of the plan, DeWine and Pennsylvania Governor Josh Shapiro ordered evacuations be expanded on Monday to encompass all homes within a 1- to 2-mile area around the derailment site, straddling either side of the state line.

DeWine's office warned that fumes released into the air from the venting operation "can be deadly if inhaled" and that anyone in the designated "red" zone around the site faced "grave danger of death." Those who remained in a "yellow" zone just beyond were "at a high risk of severe injury, including skin burns and serious lung damage," the governor said.

The statement said residents with children who refused orders to leave the evacuation zone could be subject to arrest.

Vinyl chloride is a colorless, industrially produced gas that burns easily and is used primarily in the manufacture of polyvinyl chloride (PVC) pipe and other products, according to the National Cancer Institute. It also is a byproduct of cigarette smoke.

The precise means by which crews vented the toxic gas was not explained. But the railroad said its workers had prepared drainage pits and embankments, apparently to contain residue from the release. It said state environmental officials would monitor air quality.

The company said in a short statement nearly two hours after the operation began that the "controlled breach of several rail cars has been completed successfully."

An environmental company is removing dead fish downstream from the site of the train derailment, in East Palestine
An environmental company is removing dead fish downstream from the site of the train derailment that forced people to be evacuated from their homes in East Palestine, Ohio, U.S., February 6, 2023. Reuters
Aftermath of the train derailment in East Palestine, Ohio
People enter to an assistance centre, following a train derailment that forced people to evacuate from their homes, in New Waterford, Ohio, U.S., February 6, 2023. Reuters