Fire crews from throughout Utah County are working to contain an uphill-traveling fire that had scorched 100 acres of isolated land approximately seven miles up the north side of Spanish Fork Canyon Saturday evening.

As of press time, public safety officials told the Deseret News the cause of the blaze is unknown and under investigation.A squad of 45 firefighters and five engines from Utah County, the forest service, Springville, Mapleton and Spanish Fork arrived at the scene of the blaze, which began at 6 p.m. A water-dropping helicopter is also working the fire.

The fire burned land covered in grass and oak brush, according to forest service spokeswoman Loyal Clark. "No structures are threatened," she said.

As the sun went down Saturday night, fire crews had better success at containing the fire. The blaze burned quickly at the outset, Clark said, as it moved through a grassy area. Once it reached green oak brush, it slowed considerably.

Firefighters hope to have the fire out sometime Sunday, though the heat wave sweeping the state won't make that task any easier, Clark said.