CAMBRIDGE (CBS) – About 5,000 people were evacuated from several buildings in Cambridge Friday morning because of what authorities described as a “major” natural gas leak.

It happened on Binney Street near Kendall Square just after 8 a.m. when a contractor working in the area damaged a line, according to Eversource.

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An excavation crew was digging a trench three feet down under an elevator with a backhoe when it hit the line.

“I just saw a bunch of guys running,” recalled construction worker Kenny Martin. “Usually on a construction site, you don’t see that.”

One witness said the noise was so loud it sounded like a jet engine as smoke rose from the road.

“I heard a hissing, like a really loud hissing noise and that was pretty much my idea to get out of the area,” said Martin.

Cambridge firefighters say the incident was accidental and all safety precautions were in place.

An aerial view of the gas leak on Binney Street in Cambridge. (WBZ-TV)

Streets were shut down, eleven nearby buildings were cleared out and the utility and firefighters were able to shut off the gas lines in the area.

“The evacuations included residents, businesses, daycare facilities,”  said Cambridge Assistant Fire Chief Thomas Cahill.

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Ten buildings were cleared around 11 a.m. and people were allowed to return inside.

The building where the leak happened, 100 Binney Street, still has gas on every level of the building. It is unoccupied and under construction, but workers will not be allowed back in until Monday.

Traffic is also flowing again in the area after several streets were shut down.

Shutting the gas off was no easy task.

“There’s multiple valves that are involved, shutting one value off does mean the gas doesn’t back-feed somewhere else in the system,” said Cahill.

There was no explosion following the leak and no one was injured.

The Cambridge fire department said interior and exterior air samplings away from the leak were negative.

“It’s a dangerous job we’re in, without a doubt,” said construction worker Joe Storella. “I mean you count your blessings when you go home safe.”

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WBZ NewsRadio 1030’s Doug Cope reports