Updated

A fast-moving fire erupted along the Northern California coast, burning homes, forcing hundreds of residents to flee and backing up traffic for miles on a scenic highway.

California Department of Forestry and Fire Protection officials said that the 500-acre fire was 50 percent contained by Friday evening. Cal Fire expected full containment Saturday.

While 2,000 people were ordered to evacuate earlier in the day, the improving situation resulted in Santa Cruz County closing its overnight evacuation center at 9 p.m., according to Chris Hirsch, a county spokeswoman. Residents who needed overnight housing were being sent to an evacuation center set up by the Red Cross.

A number of homes were destroyed, but there was no indication how many. Hirsch said at least nine structures had burned.

Battalion Chief Paul Van Gerwen, a Cal Fire spokesman, said helicopters were dropping water and fire retardant. About 600 firefighters had been called in to battle the blaze near Watsonville, about 90 miles south of San Francisco.

The cause of the fire is under investigation. Van Gerwen noted that multiple grass fires appeared to have merged into the larger blaze.

A six-mile stretch of Highway 1 was closed for much of the day, although southbound lanes reopened in the early evening.