Muskogee firefighters responded to a call at Raintree Apartments on Saturday to find one building with the roof of the upper units ablaze.
Muskogee Assistant Fire Chief Ben Terrell said he received the call about the fire at 500 N. David Lane at 3:37 p.m.
"All 16 units received fire damage," Terrell said. "None of the residents were injured, to my knowledge. We did have to send one firefighter to the hospital for what looked like exhaustion."
The roof on every unit on the upstairs part of the building was destroyed. Firefighters had the blaze extinguished by 6:30 p.m. and marshals began examining the building and assessing the damage.
Attempts to contact the management of the complex to find out how many residents were displaced were unsuccessful.
"Right now, it's too early to tell what the cause of the fire was," Terrell said. "The marshals are looking at the units to determine the cause and the origin of the fire."