Firefighters are trying to figure out if an apartment fire in southeast Houston was deliberately set.

The blaze broke out around 11:15 p.m. at a complex on Silver Creek Drive near Cripple Creek Drive.

When firefighters arrived, they found flames coming from an upstairs unit of the two-story building.

Firefighters were able to keep the fire from spreading to other units.

Before firefighters arrived, neighbors spotted the fire, alerted the man inside and helped him get out safely.

Investigators said the fire is suspicious because it appears it started inside an outside wall.