HOUSTON -

Cy-Fair firefighters battled a two-alarm fire in northwest Harris County Wednesday morning.

Fire officials said around 2:30 a.m. Cy-Fair volunteer firefighters arrived at an apartment complex on Jones Road at Steeplepark Drive to find heavy flames coming out of the roof.

The flames were so large that the firefighters pulled a second alarm on the fire.

Officials said the blaze burned the entire top floor of the 12-unit apartment building. 

Apartment managers and Red Cross were trying to relocate the displaced families that live in the building. 

Fire officials said one firefighter fell through the floor inside the building while battling the fire. He was treated at the scene and was able to quickly get back to work.

No one else was hurt in the fire

The Harris County Fire Marshal's Office is investigating the cause of the fire. Fire officials said they believe the fire was started by a tossed cigarette.

>>Click here to see photos from the fire.