Crews in Ohio began to release hazardous chemicals from five cars of a train that derailed amid fears of a "catastrophic" explosion on Monday at the site near the Ohio-Pennsylvania border.
What officials also called a "controlled explosion" began on Monday afternoon with reports of a loud boom and large plume of black smoke seen.
"We know the smoke looked alarming, but we are being told that everything was carried out according to plan," Pennsylvania's emergency management agency said on Monday evening.
The agency said environmental monitors had "detected nothing alarming" in air and water measurements. Pennsylvania's governor urged those within the evacuation zone to stay inside.
Scott Deutsch of Norfolk Southern Railroad said the release process entailed creating a small hole in each one of the tank cars and allowing substances to go down into a pit which is then lit on fire. "We are doing this so we control these tank cars that we have concerns with," Deutsch said on Monday.
Earlier on Monday, Ohio Gov. Mike DeWine said he approved the operation of the "controlled release" at the site in East Palestine, Ohio. The alternative — possibly waiting until the cars break down themselves — would have been more difficult to manage, according to DeWine.
"We had to weigh different risks with no great choices," he said.
Residents nearby the derailment have evacuated
Law enforcement had canvassed East Palestine to evacuate any remaining residents. DeWine issued an evacuation order on Sunday evening for residents living within a mile radius of the derailment site. In light of the operation, that evacuation order was extended to residents living in a one-mile by two-mile area from the site, which includes parts of Pennsylvania.
DeWine said the release of chemicals could be deadly if inhaled. It could also cause skin burns or serious lung damage.
The threat of a major explosion emerged Sunday night after a derailed train car experienced a drastic temperature change, according to DeWine. A "catastrophic tanker failure" could cause a blast and send deadly shrapnel to fly up to a mile away, he continued.
Air and water are being monitored for contamination
The operation follows concerns about hazardous materials such as vinyl chloride, phosgene and combustible liquids contained in the derailed cars.
The Columbiana County Emergency Management Agency said it was monitoring the air quality and sampling the water in the Sulphur Run, a nearby stream, for any contamination. As of Sunday afternoon, officials told residents that the air and drinking water were safe.
On Sunday evening, Columbiana County Sheriff Brian McLaughlin said there was "a high probability of a toxic gas release and or explosion." Local, state and federal authorities have been on site to prevent a blast.
The East Palestine City School District was closed on Monday. Several roads were also closed throughout the village of East Palestine.
About 50 cars of a Norfolk Southern train went off track in East Palestine on Friday around 9 p.m. local time. The train was eastbound heading from Madison, Ill., to Conway, Pa.
The derailment led to a days-long fire that caused a strong odor around the area, according to member station WOSU.
Ten of the 50 derailed cars contained hazardous materials — five of which include vinyl chloride, according to the National Transportation Safety Board.
In a press conference on Sunday, the agency said investigations are ongoing but preliminary findings indicate one of the rail car axles experienced mechanical issues.
The agency added that three crew members on the train were able to evacuate and no injuries have been reported.
