Noah Berger, Associated ressP
A cow grazes as a plume of smoke rises above the landscape from the Wragg fire near Winters, Calif., on Thursday, July 23, 2015. According to Cal Fire, the blaze scorched 6,900 acres and is 15 percent contained.

WINTERS, Calif. — A wildfire burning in Napa and Solano counties had calmed enough that many were allowed to return to previously threatened homes, officials said.

Evacuation orders were called off for roughly 50 of the 200 evacuated homes as firefighters stunted the growth of the blaze Thursday night, said Amy Head, state fire spokeswoman.

"The threat has diminished pretty substantially in a lot of areas," Head said. "We didn't have a lot of growth today, which is good."

Since breaking out Wednesday, the blaze has burned more than 10 1/2 square miles in drought-parched countryside near Lake Berryessa.

The most active part of the fire was burning along a mountain range in a remote area several miles from the highway that feeds into the lake park.

The fire was 20 percent contained early Friday.

The fire's cause, initially reported as a vehicle accident, remains under investigation, but the state's deep drought has helped it thrive.

"The conditions out there because of the drought have caused all of the fuel and vegetation to become extremely dry and readily available to burn, so it's definitely contributed to how quickly the fire has spread," Head said.

Lake Berryessa is one of the largest bodies of fresh water in California and while it's less than an hour's drive to California's famed Napa Valley wine country, the wineries were in no immediate danger from the fire.

"It's pretty far away from the Napa Valley," Head said, adding that people are "fine to go into the Napa Valley and do tastings."

Still, Marcia Ritz, owner of the Spanish Flat Country and Deli in Napa, said she worried about the impact the fire would have on tourism.

"We have the resorts up here, and in the summertime we depend on them," Ritz said.

Meanwhile, a new fire that broke out Thursday afternoon in the Sierra southwest of Lake Tahoe grew to 100 acres in heavy timber. The fire was burning on both sides of the American River and U.S. Highway 50, which was closed about 60 miles east of Sacramento. Containment was estimated at just 5 percent.

Bender reported from San Francisco.