Official court documents show Kelly's remains were buried at the prison where he was executed for murder in 1880. Officials allegedly moved his body to a mass grave at the Pentridge prison in Melbourne, though the location of his body became something of a mystery, The Australian Broadcasting Corp. said Sunday.

Ned Kelly entered Australian folklore as a robber and general outlaw. He made his own suit of armor to confront police in his last shoot-out, surviving 20 gunshot wounds before police finally arrested him, the BBC said.

Authorities said it will be hard to determine for certain if the remains are those of Kelly because grave robbers removed his head shortly after his burial.