(CNN) -- U.S. authorities on Wednesday charged a 64-year-old resident of Dublin, Ireland, accusing him of e-mailing numerous bomb threats to the University of Pittsburgh earlier this year.
Adam Stuart Busby -- who is under arrest in Ireland on an unrelated charge -- was charged with wire fraud, spreading false information and international extortion, according to the U.S. attorney's office in Pittsburgh.
He allegedly sent more than 40 emails, resulting in over 100 school evacuations, authorities said.
The series of threats spanned March 30 through April 21 and led to constant evacuations of buildings on campus and "an understandable source of heightened anxiety," said University Chancellor Mark Nordenberg.
Busby is also charged with threatening U.S. Attorney David Hickton.
The Department of Justice, the FBI and the University of Pittsburgh police investigated the threats.
It is unclear when Busby might be handed over to the United States to face charges.
Busby could not be reached for comment.
Ohio residents Alexander Waterland, 24, and Brett Hudson, 26, also were charged Wednesday for allegedly sending additional e-mail threats to the school and for stealing personal data, federal authorities said.
They were identified as members of of computer hacking group Anonymous. Neither could not be reached for comment.