The Oklahoma County Sheriff's Department said it was looking for someone in a black pickup truck who was seen throwing newspapers out a window after setting them ablaze.
Department spokeswoman Mary Myers said there were "no arrests, no suspects" but deputies were "working around the clock" to find anyone responsible.
Gov. Mary Fallin toured Luther, hugging residents whose homes and belongings were destroyed by the fire that swept through treetops on 24-m.p.h. winds.
"It's heartbreaking to see families that have lost so much," Fallin said after talking with some who were milling around the still-smoking debris that had been their homes. "I gave them a hug, told them I was sorry."
The fire burned just over four square miles, including an area near the Turner Turnpike, which carries Interstate 44 between Oklahoma City and Tulsa.
The superhighway was briefly closed Friday and traffic was diverted onto old Route 66, the cross-country highway that brought Luther a glimmer of life before the interstate bypassing the town was built in the 1950s.
On Saturday, those returning to their homes found charred timbers poking from the debris and the burned-out shells of refrigerators, washers and dryers.
"It makes me feel sad," said Victoria Landavazo, clutching a young child in her arms. "It's all gone. All of our family pictures, everything was there."