RIFLE, Colo. (KKCO)-- Firefighters are switching to air resources as a wildfire north of Rifle grows into more rugged land.

The Highway 13 Fire has burned more than 500 acres about 15 miles north of Rifle. It reaches from Highway 13 up into the Grand Hogback, an rough area with no roads and steep terrain.

According to BLM Public Affairs Specialist David Boyd, 75 firefighters have been working on the fire lines, and today, they will use a heavy helicopter and two single-engine air tankers to try to contain the flames.

Boyd expects winds over 15 mph to kick up more fire activity as the day goes on.

Houses line Highway 13 and the other side of the Grand Hogback, but no structures are threatened right now, and no evacuations are in place.

The cause is still under investigation.

Fire danger is still high across western Colorado, so Boyd wants to remind people to be very careful with fire this season.

The Highway 13 Fire was reported yesterday at 1:30 p.m. There is no estimate on containment.