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 said.

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 told The Associated Press. "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 was not suspected, Bruinsma said. He added that it was unclear whether the home had working smoke detectors.

"It's looking like it's just a tragic fire," he said, adding that the case was particularly difficult for crews to work on.

"No matter who you are and how tough you think you are, it's close to home for everybody," he said.

Lacy said the father told investigators that he awoke Christmas morning to the smell of smoke and then went outside to investigate.

"He sees the whole side of his trailer on fire and he calls to his wife to get the kids out," Lacy said. "Before she can get out and before he can get back in to help, the mobile home becomes fully engulfed."

Lacy said the family had just moved to Big Bear Lake in the fall, though he didn't know from where they came.

Bruinsma urged the public to have an emergency evacuation plan, practice it, and to make sure they have working smoke detectors in every room of their homes.

Big Bear Lake is a small city in the San Bernardino Mountains about 90 miles east of Los Angeles.