Police were called to West Clearfield Street in North Philadelphia, across from the Mount Vernon Cemetery, just after 9 p.m. Monday.
Officers arrived to find a small, white, closed casket.
When they opened it, they found a plastic bag containing what the Medical Examiner later confirmed to be two embalmed human organs from an infant.
No skeletal remains were in the casket.
"The coffin appeared to be a fresh coffin," Philadelphia Police Chief Inspector Scott Small said. "It was possibly taken from a funeral home or possibly dug from the ground from a fresh grave."
The casket was taken to the Philadelphia Medical Examiner's Office for further examination.
Police searched two nearby cemeteries to see if any graves had been disturbed, but saw no evidence of that.
They are contacting area funeral homes as they work to determine where the casket and organs came from, who left them there and why.