PITTSBURGH — Authorities investigating dozens of bomb threats at the University of Pittsburgh said Wednesday they’ve made significant progress with help from the public.

Information from students and community members has helped them to focus on potential suspects, said U.S. Attorney David J. Hickton, who encouraged people who think they may have information to continue sharing it with law enforcement.

The Pitt threats began in mid-February, at first targeting a landmark building at the center of campus. But in recent weeks numerous buildings, including dorms, have been threatened.

On Tuesday night, a threat was made against Chancellor Mark Nordenberg’s home.

No bombs have been found, and nobody has been injured, but police say building evacuations will continue if warranted. There have been about 25 threats, with some buildings threatened multiple times.

University police announced the arrest of a man at Pittsburgh International Airport on charges of harassment and terroristic threats but made no connection to the string of bomb threats. Pitt spokesman John Fedele told said Mark Lee Krangle, 65, of Croton-on-Hudson, N.Y., was taken into custody at 1:30 p.m. Wednesday by campus police assisted by Allegheny County police. A listed number for him could not be found and it was unclear whether he had an attorney.