(Updates number of wedding guests, days to containment)

LOS ANGELES, April 27 (Reuters) - A wildfire that began along a popular hiking trail forced 1,000 people to evacuate their homes in the hills northeast of Los Angeles on Sunday, officials said.

The cause of the 400-acre (162 hectares) fire, which started Saturday afternoon as Southern California logged near-record temperatures, was still under investigation, said Elisa Weaver, a spokeswoman for the city of Sierra Madre, about 20 miles (32 km) northeast of downtown Los Angeles.

Some 45 people celebrating a wedding at a mountain campground were lifted from the area by helicopter after the fire cut off their exit trail. No one was harmed.

Temperatures climbed above 90 degrees Fahrenheit (32 degrees Celsius) but low winds and humidity helped firefighters. The blaze was 30 percent contained Sunday evening, up from 5 percent in the morning.

"A lot of that area hasn't burned in 40 years, but the weather has been on our side," Weaver said.

If the weather continues to cooperate, the fire should be contained fully in four to seven days, Tim Davis of the U.S. Forest Service said.

Between 400 and 500 homes were under a mandatory evacuation order, Weaver said, though only a small storage shed had been burned.

About 500 firefighters from throughout the state were assigned to the fire. Water-dropping airplanes and helicopters were also mobilized.

Late last year, strong winds, high temperatures and parched brush after a record drought were blamed for spreading a series of blazes from Santa Barbara to the Mexican border that destroyed thousands of buildings and drove hundreds of thousands of Californians from their homes. (Reporting by Nichola Groom; editing by Alan Elsner)

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