NEW YORK, United States (AFP) — United States police announced Thursday that they had used modern DNA testing and genealogical analysis to identify a boy found dead in a cardboard box in Philadelphia more than 65 years ago.

The case of the "Boy in the Box" — the subject of a 2008 book — is one of the East Coast city's most notorious unsolved murders.

At a press conference, Philadelphia police commissioner Danielle Outlaw named the child as Joseph Augustus Zarelli.

His severely beaten body was found wrapped in a blanket inside the box in a wooded area of Philadelphia in February 1957.

"The boy appeared to be malnourished, and his body bore the signs of recent and past trauma. In his very short life it was apparent that this child experienced horrors that no one, no one, should ever be subjected to," Outlaw told reporters.

An autopsy concluded that the boy was aged between four and six but nobody ever came forward to claim the body, and hundreds of tips and leads failed to identify him.

Zarelli was initially buried in a potter's field, a burial site for unknown or unclaimed people.