A prisoner facing charges of attempted murder and hostage-taking escaped Thursday during a trip to a hospital in Halifax.

Jermaine Carvery, 30, got out of his leg restraint and bolted from a corrections van at the Centennial Building of the Victoria General Hospital, justice officials said.

Police are on the lookout for Carvery, who they describe as dangerous, and are urging anyone who encounters him to stay away.

Meanwhile, corrections officials are trying to figure out how their prisoner got away.

"It's very difficult to get out of a leg restraint," said Fred Honsberger, executive director of Nova Scotia Corrections Services. "We need to determine how that happened."

Carvery was wearing leg restraints and handcuffs when he was placed in the van at the Central Nova Scotia Correctional Facility in Dartmouth for the ride to his medical appointment.

When the van pulled up at the hospital at about 1:15 p.m., Carvery jumped out and ran past a guard as soon as the door was opened, Honsberger said.

The other guard was getting a wheelchair, he said. No one was hurt.

Carvery was last seen still bound in handcuffs. He was wearing civilian clothing, which Honsberger said is policy when prisoners head out for medical appointments.

Const. Jeff Carr, spokesman for Halifax Regional Police, said they were called by corrections officials at 1:40 p.m.

Ten or 12 uniformed officers were dispatched immediately, he said, and about five blocks were cordoned off as the K-9 unit swept the area.

Carvery is accused of a number of high-profile crimes in Nova Scotia, including a 2004 armed robbery at the Costco in Halifax where 42 workers were bound and gagged.

Honsberger said he has complete confidence in correctional staff and in the procedures that are in place for prisoner transfers. However, he added, changes will be made if necessary.

This is the fourth prisoner to escape or be accidentally released since December.

Michel Samson, Liberal justice critic, said this most recent incident does nothing to inspire confidence that the system has improved.

"There are security protocols that need to be reconsidered at this point and one would think the government would undertake whatever measures are at its disposal," Samson said.