The home of the University of Pittsburgh's chancellor was among the latest targets of a series of empty bomb threats plaguing the Pennsylvania school, officials said Wednesday.
The Tuesday night scare at the home of Mark Nordenberg was followed by five other threats on university buildings early Wednesday morning, according to school spokesman Robert Hill.
A total of 55 buildings on the Pittsburgh campus have received dozens of threats since February 13, he said. Some buildings have faced more than one threat.
All of the threats have since been cleared, and authorities have yet to uncover explosives in any of the incidents.
The Department of Justice, the FBI and the University of Pittsburgh police are investigating. A federal law enforcement official described the investigation as "extremely focused" but would not say whether investigators have a specific suspect or suspects.
Many of the earlier threats were written in bathroom stalls, while most of the more recent ones have been made against Pittsburgh's newspapers -- the Post-Gazette and the Tribune-Review .
The phenomenon has also affected campus life.
"I'm running on two hours of sleep," said Pitt senior Dmitry Kalika, who was evacuated from his dorm early Wednesday.
He said that just after a bomb scare, he stayed with fellow student Nick Czarnek, who is part of an emerging network that uses social media to offer temporary housing for displaced students. More than 150 apartments and dorms are listed in the forum, which was created by students and posted on Facebook.
"I think it's been pretty effective," Czarnek said.
Students and parents, meanwhile, have expressed weariness and worry about the threats.
"The first few were kind of spread out, and they were seen as a joke," Czarnek said. "But after they started increasing in frequency, now everyone is sort of creeped out."
"The phone is ringing all the time," said Czarnek's mother, Victoria, who signed up for the university's mobile alert system.
"I have been very much on edge," said Rochester resident Donna Curran, whose son is a student at the university. "It's unnerving. ... He texts me every time there is a threat."
"It's gotten to the point where it's scary," said her son, Chris. "At first, people were just annoyed."
He said that one of his professors offered to end class for the rest of the semester and calculate grades based on current performance. Another professor, he said, is conducting the class's final online as a result of the threats.