Autopsies had previously been performed on two babies whose bodies were found next to a trash-littered used car lot in Philadelphia, police said on Sunday.

The bodies of a baby boy and girl were discovered in the Kensington neighborhood just before 10:30 a.m. Sunday, authorities said. The babies were pronounced dead minutes later by a medical unit and homicide detectives were notified.

Police said Sunday night that while processing the scene, the medical examiner discovered the babies "had an autopsy performed on them by unknown medical personnel at an unknown time."

Although police originally said the babes were newborns, a spokeswoman said Sunday night that the medical examiner was "unable to provide an approximate age."

Officials said a 9-year-old boy and his 12-year-old neighbor apparently found the babies on Saturday evening and told their parents. One boy said he thought the bodies were dolls, Philly.com reported.

The boy's father said he assumed his son was mistaken, but called police after the youngster told him the bodies smelled.

Police said they were looking for occupants of a black pickup truck reported dumping trash in the weed-filled area, which is full of broken concrete, glass and trash. Detectives with the special victims unit were to canvas the area for possible video surveillance.