A resident from a building next to the two that collapsed reported that he smelled gas inside his apartment, but thought the odor could be coming from outside, Con Edison spokesman Bob McGee said.

He said the utility dispatched two crews just after 9:15 a.m. but they arrived after the explosion. McGee said the street is served by an eight-inch (20- centimeter) low pressure gas main, but would not speculate on whether a gas leak caused the explosion.

“We're working with the FDNY and checking gas lines,” he said. “We're working to isolate any leaks and make the area safe.”

A man who lives several blocks from the scene of the blast said he heard the explosion at about 9:30 a.m., ran to the window and saw flames consuming one building and smoke rising into the air.

“I was in my bedroom and the explosion went off, it kind of shook the whole building,” Eoin Hayes, 26, said. “You could feel the vibrations going through the building.”

Hayes said the fire consumed one building and then moved to the one next to it before the flames eventually subsided.

The explosion occurred very close to elevated Metro-North commuter railroad tracks. Train service was suspended to and from Grand Central on all three train lines while employees remove debris from the tracks.

The fire department said it sent nearly 170 members to the scene.