REDWOOD CITY -- A 35-year-old woman was found dead Sunday night in her apartment, and investigators were working to piece together what killed her, police said.

A man who lived with the woman, whose name hasn't been released, found her unconscious and called police to their apartment on the 1100 block of Second Avenue around 11 p.m. Paramedics attempted to revive her, but she was pronounced dead at the scene about 30 minutes later, said Redwood City police Lt. Sean Hart.

Police didn't find any gunshot or stab wounds. Hart said there were no apparent signs of foul play, but at this point investigators can't rule anything out. No arrests have been made.

Until the San Mateo County Coroner's Office makes a ruling on the cause of death, which could come in a month, detectives won't be able to say whether her death was an accident, homicide or suicide, Hart said.

So far police believe the man, whose connection to the woman wasn't released, entered a room to find the woman unconscious.

Contact Joshua Melvin at 650-348-4335. Follow him at Twitter.com/melvinreport.