The police in Pennsylvania said Danelo Cavalcante, a convicted murderer who escaped from a Pennsylvania prison more than 10 days ago, was armed and had been spotted again on Monday night.

James Mckee, a Pennsylvania State Police trooper, confirmed the sighting in a brief telephone interview on Monday night. He said he could not confirm any other details.

But in a Facebook post early Tuesday, the state police said their officers were pursuing Mr. Cavalcante in South Coventry Township of Chester County, and that he was “armed with a weapon.”

Mr. Cavalcante, 34, clambered up a wall and escaped from Chester County Prison on Aug. 31, days after he was convicted of murdering his ex-girlfriend in 2021. He has since eluded hundreds of law enforcement officers in quiet, wooded communities outside Philadelphia, stirring a relentless unease among residents.

He has been spotted several times, even as officers have used drones, dogs and helicopters to try to find and arrest him. But he was still at large as of Tuesday morning, as helicopters circled the skies above the search area.

The state police’s Facebook post asked residents to stay inside, lock their doors and windows, and secure their vehicles. The police also issued an alert to residents that conveyed the same advice and asked them to review their surveillance camera footage.

Separately, Chester County’s Department of Emergency Services issued a report of a shooting, with injuries, on Monday night. The shooting occurred after 10 p.m. on Coventryville Road, one of three roads that the state police said defined the area of their search for Mr. Cavalcante early Tuesday. But it was not immediately clear if the shooting, near Pughtown, Pa., had involved Mr. Cavalcante.

Mr. Cavalcante, a Brazilian national, is also wanted for a 2017 murder in his home country.

After more than a week of hiding out in the quiet communities south of Chester County Prison this month, he slipped through a perimeter set by law enforcement and stole a delivery van over the weekend. On Saturday night, he was seen on a doorbell camera miles away. The police are now searching an area deeper in the Pennsylvania countryside where he abandoned the van, apparently after it ran out of gas.

On Monday, officials told reporters that Mr. Cavalcante’s recent movements had changed the nature of the search, and that they worried he might try to steal another vehicle. They urged people in the area to be vigilant and warned of consequences for anyone who helped him.

State and federal authorities, including the U.S. Marshals Service, initially announced a $10,000 reward for information leading to the fugitive’s capture. The reward was later raised to $20,000. On Monday, it climbed to $25,000.

Kriston Jae Bethel contributed reporting.