(Reuters) - A convicted murderer who broke out of a maximum security prison in New York spent months exploring tunnels and pipes underneath the facility before using them to escape with another inmate, the New York Times reported.
David Sweat, 35, and Richard Matt, 49, escaped from the Clinton Correctional Facility in Dannemora, N.Y., on June 6 after they cut through their cell walls, carved a hole in a steam pipe and made their way to a manhole cover outside the grounds.
After an extensive manhunt, Matt was shot and killed by a federal agent on June 26 about 27 miles (43 km) away from the prison. Sweat was shot and apprehended two days later.
The men's escape from the maximum security prison, the likes of which are extremely rare in the United States, has prompted an investigation by the state's inspector general, who has the authority to seize documents and question witnesses.
From his hospital bed, Sweat told investigators he would wait until prison guards had done their last headcount each night to crawl down into the tunnels beneath the prison, the New York Times reported on Monday, citing officials briefed on his account.
He spent months getting to know the interior system of passages and pipes until he found some that led to the other side of the prison walls, the Times reported.
Sweat and Matt then used tools and a hacksaw to drill holes into a large pipe running through a tunnel - a process that took weeks.
Sweat told investigators that guards remained unaware of the men's work under the prison as he was "confident" that had been asleep, the newspaper said.
There was no response to an emailed request for comment to the New York Department of Correctional Services.
Two Clinton prison workers are charged with helping in the escape. Since the escape, the prison has instituted a number of new security procedures.
(Reporting by Victoria Cavaliere in Los Angeles; Editing by Raissa Kasolowsky)