LAWRENCE (CBS) – About 150 homes and businesses were evacuated in Lawrence early Friday morning due to a major gas leak at South Broadway and Salem Street.

It started around 3 a.m., affecting Andover Street to Merrimack Street and Sandborn Street to Parker Street. The entire area was also affected by the devastating 2018 Merrimack Valley gas explosions.

“The gas line where this leak occurred has been turned off and isolated. The damage to the line was caused by an isolated incident,” Gov. Charlie Baker said at an afternoon press conference. “There is no public safety threat at this point related to gas.”

There have been no fires or explosions. Lawrence Fire Chief Brian Moriarty said one person was taken to the hospital suffering from a “possible heart attack.”

The leak was caused by contractors working for the City of Lawrence who were checking water valves in preparation of road paving.

The contractors, “inadvertently closed a gas valve, puncturing an active gas main,” the Department of Public Utilities, Columbia Gas and the City of Lawrence said in a joint statement.

“Preliminarily, it appears that this gas valve should have been disabled as part of pipeline reconstruction in 2018 and was not compliant with DPU standards.”

Columbia Gas will immediately re-inspect 45 valves and bring them into compliance if necessary. The valves are located near the surface of the road and will not require excavating.

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Lawrence Mayor Dan Rivera said a detail officer was the first to notice the leak.

Columbia Gas shut off service in the area and crews went door-to-door to the 150 customers while repairs were being done. The majority of people were able to return home with their services fully restored by 3 p.m.

A Red Cross shelter has been set up at the Arlington Middle School.

“We do have to get into each house to make sure no gas has migrated into any of the homes. We will clear each of those homes. We will then shut off the gas line to that home, test all of the lines, determine if and any repairs need to be made, repair those lines and after that we will begin to restore service to customers,” said Columbia Gas of Massachusetts president Mark Kempic.

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He added that this is a different situation from last year because this is not an over-pressurization of a gas line, which is what caused the September 2018 explosions and fires.

Related: ‘Really Panicked’ Lawrence Resident Describes Evacuation

Kempic said the high pressure gas line where Friday’s leak occurred was installed just last year. The utility suspended all other work Friday to focus on the Lawrence issue.

“We have isolated the area, as of 5:08 this morning all the gas to this area was isolated and it was shut off, so we have eliminated any immediate concern,” Kempic told reporters. “We were not doing work in that area yesterday.”

Kempic also said that residents “should feel safe tonight when they go to sleep.”

Rivera said Columbia Gas leadership “has been responsive” regarding Friday’s leak. The Department of Public Utilities is investigating.

Baker On Lawrence Gas Leak: ‘It’s A Big Deal’

According to National Grid, more than 1,300 customers in the area have also lost power because electricity had to be shut off.

Two schools were closed for the day, Lawrence Catholic Academy and the Wetherbee School.

All other schools, including Arlington Middle, were open. About 250 people are at the shelter in the gym at Arlington Middle School, away from the students. One evacuee, a pregnant woman, was taken by ambulance to a local hospital as a precaution because she may have been having contractions.

The North Andover Police Department told WBZ-TV they were getting calls before sunrise for an odor of gas in town, but they believe it was coming from nearby Lawrence.

The Merrimack Valley Regional Transit Authority canceled the route 32 and 37 bus service Friday morning because of the gas leak.

“The citizens of Lawrence have been through enough. With the memory of last year’s deadly disaster still fresh, Columbia gas owes our community a detailed explanation of how this new section of pipeline has already failed,” Rep. Lori Trahan said in a statement Friday. “My office stands ready to assist those who have been temporarily displaced.”

Anyone needing help with shelter should call 1-800-564-1234.