The Greer Creek fire was about 30 square kilometres in size when this picture was taken over the weekend. (BCFS)

A forest fire in the central interior of B.C. nearly doubled in size overnight Sunday, raising concerns that about 35 homes will soon need to be evacuated.

The homes are in the Nulki Lake area.

The B.C. Forest Service says the Greer Creek fire has been fuelled by standing dead trees, high temperatures and strong winds.

By Monday morning the fire was estimated to be about 50 square kilometres in size, and about 100 firefighters were fighting the blaze.

The smoky haze from the fire could be seen as far away as Prince George, about 100 kilometres east.

Gerry Thiessen, the mayor of nearby Vanderhoof, said the firefighters seem to be losing the fight to control the fire.

"They can't do anything, it's too big and too fast. The wind is changing as well. What we noticed as a family is, we just have a small window open and that smoke was just coming through the whole house," he told CBC News on Monday morning.

Residents prepare to get out

The evacuation alert applies to the residents of about three dozen homes in the community of Nulki Lake, about 30 kilometres southwest of Vanderhoof, who have been told to be ready to leave at a moment's notice if officials issue an evacuation order.

Nulki Lake resident Mike Johnston said he is ready to go if the fire forces him out. "It's pretty smoky here this morning, I can't even see across the lake. I'm not leaving until I have to. If I have to leave by boat, I'll leave by boat," said Johnston.

Meanwhile, there are two other fires of note burning in northern B.C. both located in the Peace River region, north of Fort St. John.

In one of the fires, an evacuation alert for residents near Pink Mountain, along the Alaska Highway, has been rescinded after fire crews made good progress over the weekend.

The other fire, at nearby Beatton River, grew to 3.5 square kilometres overnight, but no homes or structures are threatened by that blaze.