Murder suspected in mass death of Irish immigrants

US historians trying to uncover a mystery surrounding the mass death of 57 Irish immigrants nearly 180 years ago have uncovered evidence they may have been murdered.

Previously, it had been thought that the group, which died within weeks of starting gruelling work on the Philadelphia and Columbia railroad in 1832, were cholera victims.

Two skulls unearthed at a probable mass grave near Philadelphia last week showed signs of violence, including a possible bullet hole. Another pair of skulls found earlier at the site also displayed traumas, seeming to confirm the suspicions of two historians leading the archaeological dig.