A steam pipe containing cancer-causing asbestos has exploded beneath a New York street sending white smoke 10 storeys high and forcing the evacuation of 49 buildings.
Five people, including three civilians, suffered minor injuries from the blast on 21st Street in Manhattan.
Officials warned people who may have got material on them to bag their clothes and shower immediately as a precaution.
On a street near the blast site, firefighters stripped off their heavy outerwear, bagged it and entered a red decontamination tent in their gym shorts and T-shirts to take showers.
“There was asbestos in the steam line casing,” Mayor Bill de Blasio said about eight hours after the explosion but “the air cleared fairly quickly after the incident”.
He added: “There is no meaningful presence of asbestos in the air at this point.”
Mr De Blasio said it could take days to check and clean the buildings, which include 28 in a “hot zone” closest to the site where the blast left a crater roughly 20 feet by 15 feet in the street.
It was not immediately determined what caused the blast in the 20-inch pipe. The mayor said no work was being done on the pipe at the time.
Daniel Lizio-Katzen, 42, was riding his bike home to the West Village when he saw the plume from the high-pressure steam explosion.
“It was a pretty violent explosion,” Mr Lizio-Katzen told the Daily News. “The steam was shooting up into the air about 70 feet. It was pushing up at such a high pressure that it was spewing all of this dirt and debris. The cars around were coated in mud. … It left a huge crater in the middle of the street.”
Brendan Walsh, 22, a student at New York University, had just got off a train and was heading to class when he saw the plume and “a large scatter of debris. … I was standing behind the police line when a Con Ed worker came rushing over and screaming at police and firefighters to push everyone north because he was worried that there could be secondary manhole explosions”.
“Everyone — including the police and firefighters who were standing by — started moving back,” he said.
Democratic governor Andrew Cuomo directed the state Department of Public Service to conduct a full investigation into the cause of the explosion and whether any “utility activities contributed to it”.
“In conjunction with that investigation, the Departments of Environmental Conservation and Labor are standing by to assist in asbestos testing, assessment and with the disposal of contaminated material,” Mr Cuomo said.
Businesses were braced for the worst as the response dragged on and police and firefighters blocked access to buildings close to the explosion, crippling their neighbourhood and their working day. Subway trains were diverted around the blast area.