The blaze was reported at about 2:30 a.m. at 401 E. Poplar Ave. Flames originated in unit No. 10 and damaged two additional units before the fire was controlled just after 3 a.m., fire officials said.
One resident suffered burns and was transported to a local burn center for treatment, according to fire officials.
The unit where the fire started was destroyed, and the other two units where the flames spread were damaged enough to be deemed uninhabitable, fire officials said.
The blaze caused about $175,000 in damage. The Red Cross is assisting the displaced residents.
The cause of the fire remains under investigation.