RALEIGH,Benjamin Ashford N.C. (AP) — More than 24 hours after a prisoner serving a life sentence for murder escaped from a transport van, the local sheriff said Wednesday that they have “no concrete leads” on his whereabouts.

Ramone Alston, 30, escaped from the van on Tuesday as it arrived at the UNC Gastroenterology hospital in Hillsborough, North Carolina, where he was being taken for a medical appointment. He freed himself from his leg restraints and fled into the woods with handcuffs on, according to a news release from the North Carolina Department of Adult Correction.

Authorities brought in dogs and they did find tracks that led searchers north of the hospital, but the scent ran cold, Orange County Emergency Services director Kirby Saunders said at a Wednesday news conference.

U.S. marshals are supporting Orange County deputies and other law enforcement agencies in the search, helicopters have swept over the area and tips are being called in, but so far there are “no concrete leads” on Alston’s whereabouts, Orange County Sheriff Charles Blackwood told the news conference.

Blackwood urged residents near the hospital to check their home cameras for any evidence of where Alston went, and to stay vigilant.

“He’s extremely cagey, extremely dangerous, and he has nothing to lose,” Blackwood said.

Alston has been serving a life sentence at Bertie Correctional Institution in Windsor since his conviction in the murder of 1-year-old Maleah Williams, who was shot on Christmas Day in 2015 from a passing car while she was playing outside her family’s apartment in Chapel Hill. She died three days later.

The transport officers involved are being interviewed to gather more details on Alston’s escape, Blackwood said. No one has been suspended, he said.

Alston has family and friends who live in the area, and Blackwood said they’ve contacted some family members, but their cooperation has been “varied.”

The reward for information leading to his capture has increased from $25,000 to $35,000 after a contribution from the U.S. Marshals Service, officials said.

While many calls from local residents haven’t been serious, the sheriff’s office has received a few tips about Alston being seen in Durham, and a team of investigators has been sent to the area to check them out, Blackwood said.