OKLAHOMA CITY - Firefighters are investigating the cause of a fires Tuesday morning that damaged neighboring vacant home in southeast Oklahoma City. 

According to authorities, the fire is reported to be near South Santa Fe Avenue and Southwest 36th Street. 

Firefighters said one of the homes is known to squatters. 

OKC fire officials said it looked like the fire was started outside. 

Even though the homes are vacant, fire officials said they've seen arson activity in the area. 

"Other homes being set fire to the exterior, we've had a couple of incidents of that. Our arson investigators are aware of it. Our crews have done a great jon of getting arson out here and letting fire investigators do their job, and start cases on each one of them, so that they can gather evidence for them," said David Meter, the acting District Chief of the Oklahoma City Fire Department. 

This is a developing story.