UPDATE: Keene fire investigators said Thursday the fire was started on an electric stove stop and was accidental. The fire was contained to one apartment, but water and smoke damage displaced the 24 residents of the second and third floor apartments. The Red Cross is assisting the displaced residents.

KEENE — Firefighters battled a four-alarm fire in a Main Street building in the heart of downtown Wednesday night.

“There are no reported civilian or firefighter injuries,” the city’s fire department said in a news release hours after declaring the fire under control.

Firefighters responded to the Exchange Block at 99-105 Main Street at 8:31 p.m. Wednesday for a fire alarm that was activated.

Upon arrival firefighters found smoke showing from the third floor rear of the building and requested a first-alarm assignment at 8:34 p.m.

The need for personnel and equipment to the scene caused firefighters to escalate that all from a second, then a third and eventually a fourth-alarm fire at 9:14 p.m.

The large building has store fronts on the first floor with residential apartments on the second and third floor.

Firefighters went to work attacking the fire that was on the third floor.

“Ladder 1 arrived and was ordered to the rear of the building and to report to the roof due to the volume of smoke exiting the roof line and the possibility the fire had extended to the attic void space,” the news release said. “Additional arriving crews were assigned to assist in the fire attack, roof operations, and searches of all floors to confirm the building occupants had exited safely.”

Four aerials ladders were used in the attack as well as five engines.

“Crews had to be rotated due to the ambient temperatures and the labor extensive work that was required to extinguish and contain the fire and damage from smoke and water,” the news release said.

The fire was declared under control at 10 p.m. and no other properties damaged by the fire.

The fire, which was contained to one apartment in the rear of the third floor, is under investigation. Damage to the second and third floor was limited to smoke and isolated water damage to the rear.

A total of 75 fire and EMS personnel responded to the scene, which included  nine on duty firefighters, 21 off duty Keene firefighters along with 45 mutual aid fire/EMS personnel.

Units from Keene Police, Diluzio Ambulance, Southwest NH Fire Mutual Aid Dispatch and fire units from Swanzey, Marlborough, Spofford, Chesterfield, Peterborough, Jaffrey and Brattleboro, VT.  assisted at the fire scene.

The American Red Cross and Eversource also assisted on scene.

Units from Troy, Walpole, Westminster, and Bellows Falls, Vt. covered the two Keene fire stations.

As of 11:30 p.m. all mutual aid fire/EMS crews had been released from the scene.

Keene Fire plans to remain on scene on fire watch till sometime Thursday morning.

Anyone with information related to the fire is asked to contact Lt. John Bates of the Keene Fire Department at 603-7571863 or via email jbates@ci.keene.nh.us.