LAWRENCE, MASS. (WHDH) - Hundreds of people who were forced from their Lawrence homes were allowed to return home 12 hours after a gas line that was replaced following the 2018 Merrimack Valley gas disaster began leaking early Friday morning.

Firefighters responding to a high-pressure gas main leak in the area of South Broadway and Salem Street around 3 a.m. found the gas traveling through the sewers, Lawrence Fire Chief Brian Moriarty said.

Residents could be seen fleeing their homes and heading to shelter as firefighters and police officers knocked on doors throughout the neighborhoods.

Columbia Gas shut off service to the area around 5 a.m. Crews then went door-to-door to check 146 meters to make sure the gas did not travel into any structures, according to Mark Kempic, president of Columbia Gas of Massachusetts.

Crews isolated and ventilated the leak before anything tragic, such as a fire or explosion, could happen, Moriarty added.

Sources told 7NEWS that a contractor working on a water line accidentally punctured the gas line.

Columbia Gas is still working to fix the “isolated incident,” Mayor Dan Rivera said at an afternoon press conference.

Rivera and Gov. Charlie Baker both stressed that there was “not a public safety risk associated with gas.”

Rivera said electricity and gas would be gradually being restored and that the majority of residents would be allowed to return home by midafternoon.

Kempic said residents have nothing to worry about and that they should feel safe when they go to sleep Friday night.

“They should feel safe tonight when they go to sleep,” Kempic said. “We continue to regret that last year ever happened and we do regret that this happened.”

A shelter was set up at the Arlington Middle School on Arlington Street, according to the Massachusetts Emergency Management Agency, who called the incident a “major” gas leak.

The American Red Cross said they assisted roughly 400 people.

One person in the affected area was transported to a local hospital with a possible heart attack, Moriarty said. It is not clear if it was related to the gas leak.

More than 1,300 residents went without power in the morning due to the emergency utility work. As of 4 p.m., less than 600 residents were without power.

Lawrence Public Schools closed Wetherbee School due to the power outages. Lawrence Catholic Academy was also closed.

This gas leak comes just over a year after the Merrimack Valley gas disaster, which left one dead, dozens injured and modre than 100 structures destroyed or damaged throughout Lawrence, Andover and North Andover.

“I don’t sleep here anymore but for all the people who do, to be woken up by gas again, a lot of them probably have PTSD from this and now we’re right back in the middle of it again,” said John Farrington, owner of Carleen’s Coffee Shop.

The series of explosions and fires on Sept. 13, 2018, had been caused by a gas line that became overpressurized during a routine replacement of old cast iron pipelines in Lawrence, officials concluded last October.

Baker said Columbia Gas would “held accountable” for their latest mishap.

Sen. Edward J. Markey tweeted that, “we need to know how a major leak in the same area could have happened just a year after the @ColumbiaGasMA disaster.”

“Lawrence residents shouldn’t have to wonder if their gas pipelines are a ticking time bomb. No American should,” he continued. “Congress needs to pass my Leonel Rondon Pipeline Safety Act to ensure that no natural gas company is allowed to shortchange safety.”

Federal officials are now recommending stronger nationwide requirements for natural gas systems.

The cause of the leak remains under investigation.

Anyone still in need of shelter should call: 800-564-1234.

This is a developing story; stay with 7NEWS on-air and online for the latest updates.

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