What to Know Con Edison, FDNY responded to a water main pipe burst and street collapse in Queens, as well as a gas main rupture, which occurred at once

The incident near Northern Boulevard and 114th Street at a Corona construction site was reported before 2:30 p.m. Friday, the utility says

The city's Department of Transportation warns of Northern Boulevard closure between 111th and 126th Street

A part of busy Northern Boulevard in Queens is shut down indefinitely after a gas main exploded and a water main burst, causing the road to collapse, fire officials said.

It's not clear what caused the mains to burst at the construction site near Northern Boulevard and 114th Street in Corona at around 2:30 p.m. Friday. There wasn't supposed to be any work going on at time because a stop-work order had been issued at the site, fire officials said.

Witnesses said they heard a large boom and then saw water bursting into the air as debris flew everywhere. The blast was so powerful it blew out windows of cars parked in the area.

"When you that have a big gas main, 24 inches, when that thing breaks, it's under a lot of pressure so it's enough to make a lot of noise," said FDNY Battalion 52 Fire Chief Thomas Wick.

Responding firefighters encountered a very heavy smell of gas, and they could see white vapor coming up, said Wick.

"You coudn't tell whether it was gas coming up under pressure, or whether it was water," he said.

The pipe explosions left a gaping hole in the foundation the size of a small house, about 30 feet in diameter and three stories down, according to Wick. DOT will have engineers on site to assess the street. Con Edison was also on scene.

No one was seriously hurt, officials said. One person who happened to be driving by was taken to the hospital with shortness of breath, Wick said.

Reggie Pegues, who lives next door to the construction site, said he happened to be at a bus stop nearby talking about how dangerous he thought the construction site appeared.

"I was very concerned, I was like, this thing looks like it's going to collapse," he said. Suddenly, "I'm smelling gas. I knew it."

The road collapsed just feet from where he was standing.

"Look at the light pole, it's bending back -- we need to call," he recalled saying. "Two seconds later, the whole sidewalk collapsed."

"The water pressure was so high in the air, it reached the sixth floor of the building," said Shaboo Washington, who works nearby.

Bernard Flores, who was driving by at the time, said, "We started freaking out. You can see in the back, the windshield got cracked as little rocks started hitting us. We got scared and did a U-turn."

The pipe breaks have undermined the westbound lanes of Northern Boulevard between 11th Street and 126th Street: "Northern Boulevard being shut down is gonna be a major, major problem here," Wick said.

The stop-work order had been issued at the site because residents called two weeks ago to complain about the excavation work for a new apartment building in the area causing cracks on the sidewalk and on Northern Boulevard, the DOT said.

"It was getting worse because you have buses, you have trucks, you have different things coming though," said Pegues.

Though Wick said it didn't appear to be any construction happening when the mains busrts, Pegues thinks differently.

"Just before we got the collapse, we heard people there working," he said. "Somebody was working some heavy equipment."

Authorities are attempting to piece together the definitive sequence of events — whether the street collapse lead to the pipe and gas line ruptures, or whether a water main break lead to the partial street collapse.