Dozens of buildings, many of them likely homes, have been destroyed in a fire burning outside the Northern California community of Manton, fire officials said Tuesday night.

Fire crews assessing the rural area determined Tuesday that 50 buildings had been destroyed, state fire spokesman Daniel Berlant said.

Officials didn't have an accurate count yet of how many of the structures were homes, but Berlant noted the buildings were spread across a vast rural area of mostly residential homes.

The blaze, which was sparked by lightning on Saturday has consumed more than 33 square miles and continues to threaten hundreds of homes.

Nearly 1,900 firefighters were battling the fire in rugged, densely forested terrain as it threatened 3,500 homes in the remote towns of Shingletown, Manton and Viola, about 170 miles north of Sacramento.

The fast-moving fire is one of many burning across the West, where dry lightning has sparked up grass, brush and timber, bringing an early start to the fire season.

Gov. Jerry Brown announced Tuesday that National Guard troops will be assisting with the firefighting efforts. The news comes a day after the Federal Emergency Management Agency said it is offering federal funds to help fight the blaze.

The fire forced the closure of Highway 44 and other roads, and prompted the declaration of an emergency in Shasta County.

Elsewhere in California, a massive wildfire in Plumas National Forest grew over the weekend due to winds. The blaze, about 120 miles north of Sacramento, has consumed 79 square miles since it started at the end of July and threatens about 900 homes.

In Mendocino County, the sheriff's office issued a mandatory evacuation for residents in Covelo due to a wildfire that has burned more than 15 square miles of thick timber and rugged terrain. One outbuilding has been destroyed and 45 homes were threatened by the blaze, officials said. The fire was sparked by lightning Saturday in a remote area, making it difficult for fire crews to access.

In Washington state, the National Weather Service warned about extreme fire danger in the eastern part of the state as forecasts called for thunderstorms with lightning.

Fire crews to the north were still hoping to fully contain a week-old wildfire that has destroyed 51 homes and 26 outbuildings, and damaged at least six other homes, fire information officer Mark Morrow said.

The fire, about 75 miles east of Seattle, has caused an estimated $8.3 million in property damage.

Lightning over the weekend also sparked smaller fires in Colorado, Idaho and Utah.