This photo of the Lillooet wildfire was taken July 25. (Kayla Pepper/Fire information officer)

A wildfire in the Yalakom Valley near Lillooet, B.C., has burned an estimated 1,000 hectares.

Officials say the fire is burning away from a cluster of 30 homes under an evacuation alert outside of town.

However, only 15 per cent of the blaze is contained, and it continues to grow.

"We did experience more vigorous fire behaviour — just a combination of the winds, the high temperatures and the lower humidity," said fire information officer Kayla Pepper. "The fine fuels out there have just dried right out."

About 125 firefighters, eight helicopters and 10 pieces of heavy machinery were working Wednesday to get a handle on the fire, which was sparked by lightning on July 21.

Crews are working the south and east flanks of the fire, which are closest to structures. The north flank is too steep for crews to reach safely.

Officials say they expect the fire to remain active over the coming days, with warm weather and high winds in the forecast.

If the fire changes direction and the evacuation alert becomes an order, homeowners are expected to leave, Pepper said. But no one will be forced out of their homes, she said.

"People have the right to leave or not, but we will not jeopardize our crews if people refuse to leave their properties during a wildfire."

Bill Spencer, who lives in one of the 30 homes under evacuation alert, said some of his neighbours may not leave, even under an evacuation order.

"Well, that's a real possibility," he said. "We know that there are people that could do that."

Meanwhile, Interior Health warns those living in the area to be aware of the health risks associated with smoke and air pollution.

People with heart or lung conditions may be more sensitive to the effects of smoke from forest fires, the authority said.

Officials are urging residents to reduce outdoor activity if breathing becomes uncomfortable.

Residents are also advised to seek out large air-conditioned areas, such as shopping malls, which generally provide improved air quality.