Rail crews in Ohio have been burning off toxic chemicals from a freight train that derailed last week, after ordering nearly 2,000 residents to evacuate their homes.
The train, operated by Norfolk Southern Railroad and consisting of three locomotives and 150 freight cars, was travelling from Illinois to Pennsylvania when it derailed shortly before 9pm on Friday.
The incident set off a huge fire that forced the evacuation of hundreds of homes in the immediate vicinity.
About 50 cars actually left the tracks, 20 of which carried hazardous materials, according to the National Transportation Safety Board (NTSB).
Public safety concerns deepened after officials said pressure-relief devices on some tankers 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”.
A plan was made to perform a controlled release of the cars under the supervision of experts and emergency officials.
The venting of vinyl chloride, a highly flammable and carcinogenic gas, began with a single explosion, followed by a steady incineration of the remaining cargo, said Sandy Mackey, a spokesperson for the Ohio Emergency Management Agency.
Live video on Monday showed a towering column of thick, black smoke rising from the accident site in East Palestine, Ohio, a village close to the Pennsylvania border northwest of Pittsburgh.
No injuries were reported from the operation or the incident itself, authorities said.
Peggy Clark, a spokesperson for the Columbiana County Emergency Management Agency, said the mandatory evacuation covered an estimated 1,900 people on the Ohio side alone.
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Mr DeWine’s office warned that fumes released into the air from the venting operation could be deadly if inhaled, while also posing the risk of skin burns and serious lung damage.
Vinvyl chloride is a colourless, 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 by-product of cigarette smoke.