DAYTON, Wyo. (AP) — More than 100 firefighters are working to suppress a wildfire that has burned more than a square mile of timber and grass in northern Wyoming.

The fire started Sunday in the Tongue River Canyon west of Dayton in Sheridan County and has burned into the Bighorn National Forest. Officials say it was human caused but they aren't ready to released details.

Fire spokeswoman Kristie Salzmann says no buildings or campgrounds are currently threatened.

However, people who have left camping trailers in the vicinity are being asked to remove them.