LOS ANGELES — Three children and their mother were killed in a Southern California mobile home fire on Christmas morning, while the family’s father survived the fast-moving blaze.

Neighbors of the home in Big Bear Lake called 911 to report the fire just before 6 a.m. Friday, according to the San Bernardino County Sheriff’s Department.

When the first deputy arrived, the home was fully engulfed and the family’s injured father was outside. The father said his family was still inside, but he couldn’t get to them because of the extent of the fire.

Firefighters arrived within minutes and were able to crawl inside and pull the mother out of the home, but she had already died, said Nick Bruinsma, assistant fire marshal for the Big Bear Lake Fire Department.

Crews were unable to reach the children because the roof collapsed, he said.

The three children killed were a 6-month-old girl, a 3-year-old boy and an 8-year-old girl, said sheriff’s Capt. Kevin Lacy, commander of the department’s coroner division. The children’s mother was 34, he said.

“This is a human tragedy,” Lacy said. “This is a horrible thing on Christmas Day. Especially when you find out there’s a baby involved. It really tugs at your heart strings.”

The father was airlifted to a hospital for treatment with burns, cuts and smoke-inhalation injuries, and his condition was unknown, Bruinsma said.

The cause of the fire was under investigation, but foul play is not suspected, Bruinsma said.