A man was arraigned in Dorchester District Court today on charges he called in bomb threats that emptied UMass Boston's Wheatley Hall last Thursday and again on Tuesday.

In both cases, the building was evacuated but no actual bomb found.

Dean Beckford, 29, of Somerville, had bail set at $20,000, the Suffolk County District Attorney's office reports.

UMass officials identify him as a senior.

According to the DA's office:

"Officers and detectives of the UMB Department of Public Safety were able to identify the phone number from which the call was placed. That number belonged to a pay phone at the Davis MBTA station. Department of Public Safety personnel worked with MBTA Transit Police to gather footage from public safety cameras at the station.

"The second call was also placed to Wheatley Hall and came in at about 12:45 pm on April 22. As with the first threat, the male caller stated that there was a bomb in the building and that people inside should leave. Investigators tracked this call to a pay phone on Tremont Street near the Park Street MBTA station.

"Based on their review of footage from Davis station, comparison of that footage from cameras on campus, and input from school faculty, UMB Police had by this time identified Beckford as a potential suspect. At about 1:20 pm, they detained Beckford as he arrived on campus."

UMass Police Chief Donald Baynard said: "Although we apologize for the inconvenience that these incidents caused for students, faculty, and staff, campus safety is always our highest priority. I commend my staff for their timely and thorough investigation that led to this arrest. I hope this will be a clear and resounding message that we take these types of actions very seriously and will aggressively investigate and pursue criminal charges when unfounded threats are made to the safety of the campus."