Thousands of residents were yanked from their homes in Andover, North Andover and Lawrence Thursday after a gas leak set off dozens of house fires. Massachusetts Gov. Charlie Baker declared at state of emergency in those towns Friday, prompting Boston and other neighboring cities to send assistance.

The gas explosions injured 25 people and killed one — 18-year-old Leonel Rondon , who died in his car when a chimney fell from a house in Lawrence and crushed his vehicle, Boston Police Department Sgt. John Boyle said.

Although the affected towns are located in Merrimack Valley, outside the jurisdiction of Boston emergency officials, city boundaries did not stop the departments from lending their support — according to Boyle, BPD responded by sending reinforcement to the affected areas.

“… we activated our emergency deployment teams and responded up to that area to assist the local authorities,” Boyle said. “We sent a contingent up to [Lawrence and Andover].”

Frustrations from community members regarding the prolonged evacuation prompted Baker to transfer control of the issue away from Columbia Gas, the company whose high pressure gas lines caused the explosions, to the New England electric and gas company Eversource, in accordance with a state law.

The Boston Fire Department sent six fire engines to Merrimack Valley and were stationed at a movie theater, said BFD spokesman Brian Alkins.

“Based on who’s in charge of the staging area in Lawrence, since it’s not Boston, they would send companies out as needed to certain areas to help with the fires or help check the gas or whatever needed to be done,” Alkins said. “That’s what the [Boston Fire Department] did.”

On Sunday morning, almost 72 hours after the initial evacuations, most residents were given permission to return their homes.