Escaped prisoner Danelo Cavalcante was spotted twice on Friday within the Chester County search area, Pennsylvania state police said, as officials appear to narrow in on the fugitive by reducing the search zone.

Authorities said these were “visual sightings” in the zone around Longwood Gardens, a public esplanade in the county. They did not provide further details.

Cavalcante, who was sentenced last month to life in prison without the possibility of parole after he was convicted of fatally stabbing his former girlfriend, slipped out of the Chester County Prison in Pocopson Township on Aug. 31.

Surveillance video showed that he stretched himself across the brick and cinderblock walls in the exercise yard and climbed to the roof. Inmate Igor Bolte had briefly escaped in a similar fashion in May, prompting the prison to install razor wire on the roof — which Cavalcante was able to evade.

A prison guard who was on duty when Cavalcante, 34, escaped has since been fired, a Chester County spokesperson said Friday. The guard, who has not been identified, violated prison policy by having a cell phone in the tower, the spokesperson said.

Around 400 law enforcement officers from various agencies have assisted in the search. A perimeter of about four square miles was being searched Saturday, down from the roughly 10-mile perimeter they had on Friday.

Officers have used heat-sensing technology, K9 dogs and helicopters as they combed through portions of Chester County. Lt. Col. George Bivens with the Pennsylvania State Police said the search had been complicated by heat and high humidity but officers “are up to the task.”

A reward of up to $20,000 is being offered for tips that lead to Cavalcante’s arrest.