The wildfire burning northwest of Fort Collins has grown to possibly 300 acres this evening and the U.S. Forest Service has called in additional help to fight the blaze Tuesday.

There are about 45 firefighters from the U.S. Forest Service, Larimer County Emergency Services and local departments are trying to contain the fire, with the help of a single-engine air tanker this afternoon, according to the Forest Service.

The agency has requested four 20-person crews, a firefighting helicopter and a heavy air tanker to assist tomorrow.

The fire is in Poudre Canyon less than a mile from Poudre Park, is burning . is burning timber, brush and grass in steep, rugged terrain near the Hewlett Gulch Trail in the Roosevelt National Forest.

Though there are homes in the area, none are immediately threatened, the Forest Service stated.

Residents have been put on standby to evacuate from mile marker 110 to mile marker 115 on Colorado 14, and areas a quarter mile north and south of the highway.

The Hewlett Gulch Trail and the Greyrock Trail are both closed, and the Forest Service has asked the public to avoid the area, because of fire-fighting operations and traffic.

Authorities have not identified a cause of the fire yet.

A smoke plume has been visible from Fort Collins all afternoon.