Flames broke out around 11:30 p.m. at the Blair Mill Village West apartments on Alison Road in Horsham Township, Pennsylvania.
Crews arrived to find flames showing from the side of one of the apartment buildings. They say the fire started on the first floor and quickly spread to the second.
According to officials, two tenants were taken to the hospital. There's no word on their conditions.
The fire damaged four apartments before being contained.
The cause of the fire remains under investigation.