A frantic manhunt was underway on Sunday for two convicted murderers who broke out of New York's biggest maximum-security prison by cutting through cell walls with power tools and escaping along tunnels.

Killers Richard Matt, 48, and David Sweat, 34, sneaked out of the all-male Clinton Correctional Facility in Dannemora sometime between Friday night and early Saturday. Police said the discovery was made during morning roll call and warned that the duo should not be approached.

The pair reportedly left a taunting note behind saying: "Have A Nice Day."