GRAND RAPIDS, Mich. (WOOD) — The Grand Rapids Fire Department has determined the cause of an apartment fire that injured three firefighters last month.

Fire broke out on Dec. 11 around 9 a.m. at a Ridgewood Apartments complex in the 2100 block of Woodburn Drive. Kentwood and Grand Rapids fire departments battled flames fueled by high winds, finally extinguishing the fire.

On Thursday, investigators said that the fire was accidental. It was found to have started in a gas-forced furnace, then spread through several apartments. The intensity of the fire was made worse by high winds, GRFD said.

No citizens were harmed, but a firefighter, lieutenant and captain were injured at the scene. They were treated for a broken ankle, trauma from a section of ceiling falling and smoke inhalation respectively.

A total of 24 apartment units had either fire damage or water damage, GRFD says.