Los Angeles (CNN) -- Investigators found more human remains Thursday at a water treatment facility in Carson, California, a sheriff's official said.
Los Angeles County Sheriff's Deputy Irys Alvarez said authorities think the remains are related to body parts found days ago at the same plant and at another treatment plant 30 miles away.
Investigators believe the body parts found so far -- a head, torso, legs and arm -- belong to the same woman, and that she was likely slain. But they haven't identified the woman yet or determined what caused her death.
"We're treating this as a homicide right now because of the fact that nobody can fall into the system," Lt. Michael Rosson of the sheriff's department said Thursday. "So (it's) one of two things: It was a nefarious act where somebody was killed and placed in that system, or somebody passed away and somebody panicked and placed them in that system."
Officials think the body entered the water system intact through a storm drain and then was dismembered as it traveled through the fast moving water to the plants.
CNN's Kyung Lah and Diahann Reyes contributed to this report.