Ground search called off for convicted attempted cop killer David M. Watson, 28, was sentenced to more than 100 years in prison.

 -- The ground search for an escaped inmate convicted in the attempted murder of a Delaware cop was called off today, police said.

David M. Watson, 28, escaped Friday morning from a van that had been driven from the Wicomico County Corrections Center to the Clifton T. Perkins Hospital Center in Jessup, Maryland, according to Howard County Police Department spokeswoman Sherry Llewellyn.

The ground search was suspended after police had exhausted "all search efforts in the immediate area," Howard County police said this afternoon. They are still investigating in an attempt to locate him, the police statement said.

The escape happened on the edges of the hospital grounds Friday around 9:40 a.m. local time, Llewellyn said. When a guard opened the door to the van, Watson pushed the guard down and ran into the woods, Llewellyn said.

Authorities believe Watson somehow got out of his handcuffs and waist chain while in the van.

Llewellyn told ABC News on Saturday that police officers have been "working around the clock" to find Watson since he escaped. Police searched the area around Clifton T. Perkins hospital in Jessup with bloodhounds, K-9 units and helicopters with heat-seeking technology throughout the day Friday, overnight and into Saturday morning, the Howard County PD statement said.

"Investigators are not releasing specific details about the search area or the number of officers for investigative reasons. We also have been conducting investigations in Delaware and Wicomico County, as the suspect has ties to both areas," she told ABC News.

Llewellyn said there have been no confirmed reports of sightings of Watson, who was sentenced of more than 100 years in Delaware for attempted murder. He reportedly shot at a Delaware police officer's house.

The Howard County Police Department has released several pictures of Watson, showing him with and without glasses as well as his numerous tattoos, in an effort to help the public identify the fugitive.

Watson is also facing charges in Wicomico County, Maryland, for multiple counts of attempted murder.

A Maryland judge reportedly found Watson not competent in 2014 to face trial on the attempted murder charges in Wicomico County. He was being transported to the hospital to undergo a regular six-month psychiatric evaluation as a condition set by the judge, according to the Baltimore Sun.

Wicomico County correctional officers had reportedly picked up Watson in Delaware on Thursday.

Police do not know whether Watson has any outside help or whether he has left the area. Authorities lost sight of him as he ran into the woods but they were able to pick up a canine trail, so they know in which direction he was headed, Llewellyn said.

ABC News' Lucien Bruggeman, John Verhovek and Morgan Winsor contributed to this report.