A helicopter drops water on one of the hot spots at the Jackass Mountain fire, near Lytton, B.C. (CBC)

The forest fire burning at the base of Jackass Mountain in the Fraser Canyon near Lytton, B.C., has not grown after dozens of extra firefighters were deployed to attack the blaze, a fire official said Wednesday night.

Elise Riedlinger, a provincial fire information officer, said even though the fire has been contained at 130 hectares, crews are still having difficulty reaching some parts of the blaze.

"We do have a small portion of the fire, about 20 per cent, that is very difficult to access," she told CBC News Wednesday night.

"At this point, we cannot get ground crews at it, so we are just using the air tankers. So, that is going to be a challenge, getting to that part, but we are very happy with the fact that the size of this fire has not grown at this time."

The Jackass Mountain fire, burning south of Lytton, which is about 100 kilometres southwest of Kamloops in B.C.'s southern Interior, was sparked Sunday when a motorhome caught fire.

The fire was reported on Tuesday night to be much smaller but crews mapped the size accurately Wednesday morning using GPS technology, Riedlinger said. It was then listed as 130 hectares in size Wednesday morning, a rise from 60 hectares overnight.

No homes were threatened, but the nearby Trans-Canada Highway was temporarily closed because boulders were crashing down on the road, she said. The highway was opened to single-lane alternating traffic by Thursday morning.

The boulders were loosened as the fire burned ground cover on the steep terrain above, fire information officer Jeanne Rucker said.

Lightning storms spark other fires

As many as 150 forest fires were burning in British Columbia on Wednesday after a series of lightning storms swept over the southern and central Interior on Tuesday.

A 20-person crew was battling a four-hectare fire sparked by lightning in Gillard Creek in South Okanagan Mountain Park.

Most of the fires were small, but provincial fire information officer Kim Steinbart said a few are still being targeted with an initial attack crew of three people.

Fire assessment teams consider the location, the proximity to homes or property and the manpower available when they prioritize fire resources, Steinbart said.

They also consider whether the fire is burning in pine-beetle-infested forest, she said, because those fires tend to burn hotter and faster.

With files from the Canadian Press