Police in the US are set to reveal the identity of a young boy whose battered body was found stuffed inside a cardboard box almost 66 years ago.

Detective work and DNA analysis has helped authorities in Philadelphia learn the name of the youngster, known to generations of locals as the “Boy in the box”.

His name will be announced later on Thursday.

The case is the city’s oldest unsolved murder.

The boy’s naked, badly bruised body was found on February 25 1957 in a wooded area of Philadelphia’s Fox Chase neighbourhood.

Believed to be between four and six years old, the youngster had been wrapped in a blanket and put inside a large JCPenney bassinet box.

He was malnourished and had been beaten to death, police say.

The boy’s photograph was put on a poster and plastered all over the city as police worked to identify him and catch his killer.

Detectives pursued and discarded thousands of leads — that he was a Hungarian refugee, a boy who had been kidnapped outside a Long Island supermarket in 1955, a variety of other missing children.

They investigated a pair of travelling carnival workers and a family who operated a nearby foster home but ruled them out as suspects.

An Ohio woman even claimed her mother bought the boy from his birth parents in 1954, kept him in the basement of their suburban Philadelphia home and killed him in a fit of rage.

Authorities found her to be credible but could not corroborate her story.

All the while, the boy’s missing identity gnawed at police officials, generations of whom took up the case.

Set to appear on Thursday are police commissioner Danielle Outlaw along with other law enforcement officials, as well as a genetic genealogist and the co-founder of a group of professional sleuths, called the Vidocq Society, which took up the case 25 years ago.