The Wolf Den Fire burning northwest of the Grand Valley in Utah continues to grow by adding thousands of acres overnight.

Fire officials say it grew from 10,000 acres Saturday to 15,800 Sunday. It is burning in very remote terrain, we are told, about 35 miles south of Vernal, UT, and nine miles west of the state border.

Officials say no structures or homes are being threatened and no evacuations have been ordered. They say there is a high pressure gas line in the area, but they don't expect to need to shut it down.

Officials say smoke may be visible again Sunday in the valleys.

The Wolf Den Fire sparked Friday and is 0% contained. Officials believe lightning is to blame.