A massive manhunt was underway Saturday for two convicted murders who escaped New York’s largest maximum-security prison Friday night or early Saturday morning.

David Sweat, convicted in the 2002 murder of a sheriff’s deputy, and Richard Matt, 48, convicted in the 1997 homicide of a New York businessman, were found missing from the Clinton Correctional Facility, located in Dannemora, N.Y., near the Canadian border, during a routine bed check early Saturday morning, according to Reuters and the Rochester (N.Y.) Democrat and Chronicle.

Gov. Andrew Cuomo inspected the prison Saturday, posting a photo on Twitter showing him retracing their escape route.

Prison officials told the Plattsburgh Press-Republican that the two men escaped through sewer lines. Officials say they found an “external breach” of the prison’s facilities that allowed the men to escape.

Authorities said that Sweat and Matt are dangerous and should not be approached.

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