RIVERSIDE COUNTY—Crews battling a 6,400-acre wildfire in northern Riverside County scrambled to burn off heavy brush near homes by setting a series of back fires before the expected resurgence of Santa Ana winds early Thursday morning.

The blaze, which erupted at about 3 p.m. Wednesday, threatened about 100 homes in a sparsely populated, rural area between the 60 Freeway and Interstate 10 near the city of Moreno Valley, about 60 miles east of Los Angeles. Authorities closed the 60 Freeway near San Timoteo Canyon, where motorists sped within yards of a huge wall of flames before access was blocked.

Paul Walker watched late Wednesday as firefighters rushed to put out a hot spot about 100 yards from the single-story brick and stucco home he shares with his wife and 94-year-old grandmother. The fire was ignited by an ember from one of the intentionally lit back fires.

Walker, 40, said he wanted to evacuate but firefighters assured him he would be safe and that it would probably be more difficult to move his grandmother than remain in his home, which has a kidney shaped pool and is tucked up against a hillside.

“The captain assured us the structures wouldn’t burn,” said Walker, a general contractor. “Everything they said would happen is happening just like they said it would.”

The fire consumed about 6,400 acres of brush in nine hours and was about 5 percent contained early Thursday, said Jason Neuman, a fire captain with the California Department of Forestry and Fire Protection/Riverside County. In some places, wooden guard rail posts burned like enormous matches after the fire had jumped across rural roads.

There were 500 firefighters on the scene, with 60 engines, seven bulldozers, four air tankers, and six helicopters. No injuries were reported or structures lost.

Cool temperatures had set in and 25 mph winds had died down, but fire officials said they expected Santa Anas to begin blowing again from the east Thursday morning.

Approximately 100 homes and five commercial properties were threatened, said Patrick Chandler a spokesman for the California Department of Forestry and Riverside County Fire Department. Residents of about 20 homes in the northeast Moreno Valley, closest to the fire, were encouraged to evacuate, said Dennis Gutierrez, a spokesman for the Riverside County Sheriff’s Department.

Most of those residents had left by late Wednesday, said Jennifer Johnson, 20, whose friends and family helped her pack up her parents’ two horses, two sheep, rooster, peacock and dog as the flames drew closer to her home.

“I’m getting real worried that it’s so close.There’s been fires here before and it’s gotten close before but I’ve never seen all of our neighbors go,” Johnson said as flames raged no more than half a mile from her back yard.

Earlier Wednesday, a wildfire that erupted in Mexico jumped the U.S. border and burned uncontrolled across about 2,640 acres.

About 1,640 acres on the U.S. side of the border had burned, according to the California Department of Forestry & Fire Protection. The fire was 10 percent contained by Wednesday evening, officials said. The fire in the Tecate Peak area was not threatening any structures.

The blaze was sparked by a structure fire in Mexico that spread to the brush, officials said.

Another fire broke out about 5 a.m. Wednesday in the Barrett Junction area of eastern San Diego County and burned 50 acres before it was fully contained about 11 a.m., Hagen said. The cause of the fires was under investigation.

Wind gusts up to 60 mph in canyon passes, warm weather and low humidity prompted the National Weather Service to issue red flag warnings for much of Southern California, meaning conditions favor fires growing rapidly.

Firefighters continued to put out hot spots from the 24,175-acre Topanga Fire that was 100 percent contained Tuesday, said Los Angeles County Fire Inspector Ron Haralson said.

The fire started Sept. 28 and destroyed three homes, but a well-coordinated response helped firefighters save thousands of houses.

In San Bernardino County, a 935-acre fire burning in rugged terrain in and around San Bernardino National Forest was 85 percent contained Wednesday and authorities expected its size to remain unchanged, said Robin Prince, a forest spokeswoman.

Officials said the fire was expected to be fully surrounded by Friday evening.