Authorities are looking for information on a recent string of small wildfires in Oak Creek Canyon.
The four fires set Monday and Tuesday in brush and pine needles were extinguished at less than a tenth of an acre each.
Coconino National Forest spokesman Brady Smith says authorities believe they were set deliberately along both sides of U.S. Highway 89A.
Authorities are asking the public to report any suspicious activity in the area at the time.
A reward of up to $1,000 is being offered for information leading to an arrest.