Authorities said Thursday that fires and explosions that broke out in 70 locations in northern Massachusetts may have been caused by gas pressure.

Massachusetts State Police tweeted that the fires broke out across a wide swath in the city of Lawrence and the town of North Andover.

The state police described the incidents as gas explosions and structure fires and said they were also reported in the town of Andover. State officials told residents who have gas service from Columbia Gas of Massachusetts to evacuate their homes immediately and said gas lines were being depressurized by the company.

Two people, including a firefighter, sustained non-life-threatening injuries, said town spokesman John Guilfoil. Initially , officials had said three people were injured.

Guilfoil said six people in Andover were taken to hospitals by paramedics as a precaution because they had preexisting conditions.

The Andover Police Department said in a statement that 35 fires in town have been extinguished.

"At peak, 18 fires were burning at the same time," officials said in the statement.

Lawrence police Chief Roy Vasque told The Eagle-Tribune, which covers the Merrimack Valley, that he’d “never seen anything like this.”

“It’s bad,” he said.

The state police tweeted that local authorities and state troopers were helping evacuate residents to a senior center and a middle school while detectives and others investigated multiple scenes.

“Far too early to speculate on cause,” the state police tweeted, adding that a joint investigation will be conducted when the situations is stabilized.

The mayor of Lawrence said via the state police Twitter account that all residents of South Lawrence should evacuate Thursday night "because of a planned power shut down."

A spokesperson for Columbia Gas told NBC News that the company is advising people who smell gas in the Lawrence area to evacuate, get to a safe location, and not to open or close any windows or doors.

Gov. Charlie Baker tweeted that he's urging residents to follow instructions from local officials about evacuations and to suspend their gas usage.