A fire at a vacant two-story house in Westlake spread to adjacent apartment buildings early Monday, displacing 21 residents.

The blaze began around 1:20 a.m. in the 200 block of South Reno Street, according to the Los Angeles Fire Department.

More than 150 firefighters responded to the fire, which spread to apartment buildings on either side of the vacant building. Residents in both apartments had to evacuate as a result.

Brandon Page, one of the displaced residents, said he was sleeping when he heard a woman outside shouting “fire.“

“She couldn’t really get her voice to travel so basically yelled for everyone to get up, and that was about it,” he said.

Firefighters made an aggressive attack, but a gas leak or gas line issue in one of the apartments added to the difficulty in combating the flames.

Eventually, firefighters were able to extinguish the flames in just over 70 minutes. One person was treated for minor smoke inhalation at the scene. No other injuries were reported.

Photos provided by the Fire Department shows the extent of the damage inside the burned and now uninhabitable apartments. The vacant house, meanwhile, was destroyed.

Firefighters remained on scene hours later removing piles of burned debris to clear a pathway so Southern California Gas representatives can survey the damage.

Earlier, firefighters searched the area with cadaver dogs to ensure no one was injured or dead inside any of the burned structures.

American Red Cross officials are assisting affected families.

The cause of the fire is under investigation.

Residents told KTLA that the house where the fire started was supposed to be vacant, but some have called police before to report trespassing.