Posted By: Channel 8 Eyewitness News

ABC News - Firefighters in Massachusetts are battling dozens of fires believed to have been caused by gas explosions.

The Massachusetts State Police Watch Center has responded to 39 different addresses spread across dozens of block in Lawrence, Andover and North Andover -- in Massachusetts' Merrimack Valley, the department wrote on Twitter.

The town of Andover has put out 35 fires, Andover Fire Chief Michael Mansfield said in a statement. While all of the fires there have been put out, firefighters will still remain there overnight, Mansfield said.

At least six people were treated at the Lawrence General Hospital for fire-related injuries, the hospital announced on Facebook. Two patients are in critical condition, and the hospital is preparing for more casualties, it said.

It is unclear if those victims include three people who were injured in Andover, including one firefighter and two civilians.

Evacuations are taking place in multiple neighborhoods where residents have smelled gas, according to state police.

Authorities also warned residents in the area who are served by Columbia Gas to "evacuate their homes immediately," as gas lines are currently being depressurized by the company.

Power will be shut off in all three towns, authorities said.