A mother was arrested Thursday for investigation of murdering her four daughters after firefighters found the girls dead in sleeping bags and blankets and a can of accelerant in the house.

The four, ages 5, 7, 11 and 12, apparently died of smoke inhalation.Sandi Nieves, 34, was arrested and awaiting formal murder charges, said Deputy Joan Raber of the Los Angeles County Sheriff's Department. She was hospitalized for smoke inhalation after Wednesday's fire and was in satisfactory condition.

Authorities didn't release many details of the arrest, but Raber said "at least one fire was set in the home and a container of accelerant was found."

The woman's son, David Nieves, 14, was also treated for smoke inhalation.

Investigators became suspicious shortly after firefighters responded to the woman's 911 call Wednesday, saying her house was full of smoke and she couldn't wake her sleeping children.

When firefighters arrived, the woman was calm, and she and her son were not burned. Neighbors said they saw smoke but no flames.

"She was waiting for them, opened the door for them, had a cellular or cordless phone in her hand and she said, `There's four victims inside,' " neighbor Jim Jernigan told KCAL-TV.

Firefighters found the four girls in their pajamas, tucked into blankets and sleeping bags as if they were at a slumber party.