REDDING (AP) — A series of red flag warnings issued Tuesday had fire officials concerned about containing two major wildfires in Northern California.

The high-speed winds predicted in the warnings, coupled with low humidity, could stall efforts to stop the once-massive Ponderosa Fire, which was 96 percent contained, state fire spokeswoman Julie Hutchinson said.

"On one hand, the fire is slowing down, but on the other hand, with these winds coming in, that's going to hinder our efforts to get that last bit of containment," Hutchinson said.

Elsewhere, authorities in northwest Siskiyou County ordered about 300 residents in Seiad Valley to evacuate as a fast-moving wildfire threatened more than 80 homes.

"We're going door to door and letting people know that it's time to go," Siskiyou County sheriff's spokeswoman Jayme Lynch said.

The Ponderosa Fire was burning about 150 miles north of Sacramento after chewing through more than 43 square miles and destroying more than 142 structures since it started nearly two weeks ago.

Another red flag warning involved a fire in Plumas National Forest that was 71 percent contained after it scorched more than 114 square miles.

With more than 1,500 firefighters, 140 engines and numerous helicopters battling the blaze, crews were optimistic it could be contained by Friday.

"That's the plan," fire spokesman John Daugherty said. "We want to have a full line around it and hope that it won't jump and take off again."

However, Daugherty said there could be problems, as strong winds approached the southern rim of the steadily burning blaze.

"The fire will continue to burn actively, but we're not expecting any more growth," Daugherty said. "Again, this could be another test."

The warnings could be in effect through Wednesday.

The fires were among eight major blazes actively burning across the state, Hutchinson said.