Four international prisoners escaped from a jail on the Indonesian island of Bali after apparently digging a 20-by-28 inch hole in a wall that connected to a 50-foot waste tunnel which led outside to a busy street.

The escape was discovered by guards at Bali’s crowded Kerobokan prison during an 8am check of the inmates.

Tony Nainggolan, the head of the prison, said he believed the hole – which was hidden by a cement cover - took at least a week to build.