OKMULGEE COUNTY, Oklahoma - Grass fires in rural Okmulgee County have kept several fire departments busy, and investigators are looking into whether they were started on purpose.

Okmulgee Emergency Management said crews have been fighting eight different fires since Thursday afternoon. They believe five of those fires were intentionally set.

The fires are contained as of around 9:30 a.m. Friday, but they've have already burned 1,500 acres.

Some of the fires - like the Nuyaka fire - are in rugged, rocky terrain, according to the Oklahoma Forestry Services. Beggs firefighters were out doing some back burning northeast of Nuyaka.

Beggs Firefighter Mickey Sowell said he's only gotten two hours of sleep because as soon as they would get the fires out, they would suspiciously restart hours later.

"It's very frustrating to us because, you know, we come here and put a fire out and we go four or five miles down the road, or on the other side of town, or somewhere else, and they come in behind us and start another fire, you know," he said.

With a high fire danger, Okmulgee County Emergency Management said they hope the fires will stay contained.