CONCORD, N.H. (AP) _ Authorities searched Concord Hospital on Saturday after a caller to a radio station said a bomb had been planted at the hospital, raising tensions in a city where two bombs were found at libraries days earlier.

No bombs were found after a room-to-room search, authorities said.

City and state buildings in Concord were closed for the weekend, and many public events were canceled or moved to other parts of the state.

Authorities asked residents statewide to be on alert because the bomber has a grievance with the state and there are state government buildings throughout New Hampshire.

FBI Special Agent Barry Mawn said the bomber's last communication with authorities was that two more bombs would be placed Saturday at undisclosed locations. The man has demanded money, authorities said.

Around 6:30 p.m. Saturday, swarms of police went to the hospital, about a mile from downtown Concord where the two bombs had been found.

Police would allow only critical care patients and employees to enter the hospital. The hospital had been scheduled to X-ray children's Halloween candy.

The man has contacted authorities several times since the bombs were found Tuesday not far from the Statehouse. The first bomb started a fire on a bookshelf at the Concord library.

The second, at the state library, was connected to a small propane tank but did not go off. Officials said both were crudely made pipe bombs designed to injure people, not damage buildings.