PLACERVILLE (CBS / AP) — Firefighters are taking advantage of rainy weather to make progress on a massive wildfire threatening thousands of homes in the Sierra Nevada foothills of California, authorities said Thursday.

A huge fire burning east of Sacramento grew slightly overnight to nearly 150 square miles, but containment increased to 43 percent on Thursday morning, according to the California Department of Forestry and Fire Prevention.

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“The rain is definitely allowing the firefighters to make progress on containment,” said Dana Welsh, a spokeswoman for the U.S. Forest Service.

But there are still large areas of the fire that are not contained, so the blaze could still spread when the rain stops, Welsh added. There is no estimated date for full containment.

Rain fell over parts of the fire area throughout the day Thursday, when the National Weather Service issued a flash-flood warning for the region. There is a chance for more rain through the weekend.

The rain should help firefighters expand containment lines, but it could also lead to mudslides and slippery roads that could make firefighting more dangerous, Welsh said.

More than 8,000 firefighters, some coming from as far away as Alaska and Florida, were battling the blaze, which has destroyed 12 homes and threatens another 12,000 near the town of Pollock Pines.

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Evacuees from Swansboro, a mountain community of about 400 homes, were allowed to return Wednesday night. About 2,800 people overall had been evacuated, but it wasn’t immediately clear how many remained.

Wayne Allen Huntsman, 37, has been charged with starting the fire. He has pleaded not guilty to arson and remains in jail on $10 million bail

The fire has become the second priciest blaze in California this year, costing more than $50 million to fight since it began nearly two weeks ago. The state spent more than $85 million fighting a fire in Klamath National Forest along the California-Oregon border.

The blaze is one of nearly 5,000 wildfires in California this year, a 26 percent increase compared with an average year of about 3,900.

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