The fire started around 7:50 a.m. inside a house on Princeton Street in an area called Cherryland. Firefighters found the victim's body a few minutes later after they put the fire out.
"There's no indications as of yet that there's any foul play," said Colby Staysa of the Alameda County Sheriff's Office. "It's going to require investigative work to determine if this was an accidental or a malicious fire."
The sheriff's crime lab team plans to search the home for evidence once firefighters determine it's safe for them to do so.
The victim has not been identified.