Police were called to a parking lot of a medical complex on Alessandro Place at 2:55 p.m. Sunday.
They found a woman in her late 60s there and she was pronounced dead at the scene.
"It appears she's been there for at least several hours," said Lt. Jesse Carrillo of the Pasadena Police Department. "A witness who happened to be walking through the parking lot noticed and called police."
Detectives said there was some bruising on the body, but no obvious cause of death. The incident is being investigated as a suspicious death.
"We have no idea at this point whether this is some type of medical episode, there was some type of assault. We just don't know, but we're not ruling anything out," Carrillo said.
Authorities said they're searching for clues that will help them determine if the woman was the victim of a crime.
"We'll canvas the entire area here and take it further out, hopefully we can locate cameras within a path that she may have traveled, who she may have been accompanied with, was she alone, that sort of thing still needs to be looked into," Carrillo said.