PHILADELPHIA » The Philadelphia Medical Examiner’s Office said Monday that the bodies of two newborn babies found over the weekend were “medical specimens.”

The bodies, of a girl and a boy, were preserved in formaldehyde and showed signs of surgical examination, said Jeff Moran, a spokesman for the medical examiner’s office.

“They were medical specimens such as one might find in an academic institution,” he said. “Now the question really is, where did they come from, and why were they disposed in this way?”

That’s what police were working to determine Monday, as investigators said they planned to review security footage from the area.

On the 1800 block of N. Palethorp Street, the alley where the babies were found, neighbors Theresa Cabeza, and John DeShields left messages at a makeshift memorial set up in the trash-strewn street.

Cabeza lives a block away on Hancock Street. She grew up in the neighborhood, and said that even as a girl, she avoided Palethorp Street.

“It’s always been isolated. I was always afraid to go down it,” she said.

DeShields, who owns a garage that abuts the alley, said it has long been used for dumping. Trash and discarded lumber lined the narrow street. Weeds grew 7 and 8 feet tall in an abandoned lot facing the alley.

“They need to shut this block down,” DeShields said Monday. “It’s good for nothing.”

News of the babies’ discovery spread quickly through the neighborhood Sunday, Cabeza said.

“To have this happen in your backyard hurts,” she said. “It just breaks my heart.”

Walking her dog Monday morning, she turned, for the first time, down Palethorp. She spotted the makeshift memorial at the site where the babies had been found — prayer candles, stuffed animals and a sheet with messages from anonymous mourners: “Rest in peace, little angels.” “Love you both.”

She stopped by the grocery store later for a bouquet of flowers to place in the alley. The tag read “Just because.”