FULLERTON, Calif. -- Three adults were found dead inside a Southern California home after a child called 911 to report her parents had "died," authorities said Saturday.

The child placed the call about 8:20 a.m. and officers were dispatched to a home in Fullerton, 42 kilometres southeast of Los Angeles. Inside, first responders discovered two men and a woman dead.

Two children were found unharmed, police said.

"Anytime someone loses their life it's a tragedy," police Sgt. Jon Radus said. "It's even more of a tragedy when children are involved."

Radus declined to release the children's ages or their relationship to the three adults found inside the home, citing the ongoing investigation.

He said there were obvious signs of trauma to the bodies but would not release any details on how the adults might have died. Authorities were still working to determine their cause of death.

Investigators were classifying the deaths as a multiple homicide. In a statement, the Fullerton Police Department said the agency has "committed all its resources to identify who is responsible for this act."

Radus said authorities were working to obtain a search warrant to continue their investigation at the home. He said investigators were still trying to determine whether an outside suspect was responsible for the deaths.

"We don't believe the community is currently in danger at this particular time," he said.

Neighbours said a couple with two children lived in the home and that the parents were often seen sitting outside. The home sits on a block of single family residences in a largely middle class community.