John Hollenhorst reporting

Crews are working to put out a fire on the north side of Millcreek Canyon. Investigators say it may be arson.

More firefighters are moving in to attack the flames, tonight, and possibly hit them with bucket drops in the morning.

Fire broke out Monday evening near a popular hiking and biking trail. For those familiar with Millcreek, it's on the pipeline trail north of the highway, just west of Rattlesnake Gulch.

As of Monday night, the fire had burned a couple of acres.

Robert Sanders/ Wasatch Cache National Forest: "Right now the fire has laid down. It's no threat at all to structures."

There was no lightning in the area, and authorities strongly suspect arson.