David Sweat, 35, remained at large three weeks after taking flight from the Clinton Correctional Facility in Dannemora, New York. His accomplice on Friday was shot dead by authorities near Malone, New York.
After Richard Matt was killed by US Border Patrol officers, a tight security perimeter was set up in the area, where Sweat was believed to be holed up.
About 1,200 federal, state and local law enforcement officers, were searching through a 22 square-mile (57 sq km) area along a highway between the towns of Malone and Duane in northern New York, New York State Police said in a statement.
At checkpoints on the zone's perimeter, rifle-carrying officers stopped vehicles. As darkness approached, halogen lights illuminated makeshift checkpoints.
Police in vehicle caravans spent the day passing over roads, as officers with dogs combed the ground and helicopters patrolled overhead.
Franklin County Sheriff Kevin Mulverhill spoke hopefully about finding Sweat, who was sentenced to life without parole in 2003 for killing a New York sheriff's deputy.
"After three weeks, he would have to be fatigued,” Mulverhill said. "He’s not getting regular meals, not getting good sleep."
Authorities declined to say why they thought Sweat was still in the general area where Matt was killed. Malone is 27 miles (43 km) northwest of the Clinton prison where the convicts were discovered missing on June 6.
Police tracked Matt to the Malone area, just south of the Canadian border, when two burglaries were reported this week at backwoods cabins.
On Friday, after Matt apparently fired a shot at a passing camping trailer, officers spotted and confronted him outside a cabin, New York State Police Superintendent Joseph D'Amico told reporters, Reuters reported.