Toxic chemicals are "controlledly released" from derailed train cars by Ohio workers.
On Monday at the scene near the Ohio-Pennsylvania border, workers started releasing dangerous chemicals from five carriages of a derailed train as they feared a "catastrophic" explosion.
Although the smoke appeared to be a serious problem, Pennsylvania's emergency management office reported on Monday night that everything had gone according to plan.
According to Scott Deutsch of Norfolk Southern Railroad, each of the tank cars had to have a small hole made in it as part of the release procedure.
The operation of the "controlled release" at the location in East Palestine, Ohio, was authorised, Ohio Governor Mike DeWine announced earlier on Monday.
According to DeWine, breathing in chemical discharge might be fatal. Additionally, it might result in severe lung damage or skin burns.