Graham says he's confident that Pitt officials are doing what needs to be done to protect students and find the person responsible.
"It seems that they're taking all the appropriate steps," he said.
The threats have caused some professors to move classes outdoors or offer them online and have led some students to stay off-campus. The university, located a few miles from downtown Pittsburgh, has about 3,800 full-time faculty members who serve 34,000 students.
The university is urging faculty members to make arrangements for students to make up classes or exams missed because of evacuations, but it says there are no plans to end the semester early.
No bombs have been found, and nobody has been injured, but police say the building evacuations will continue if warranted. There have been about 25 threats targeting numerous buildings, with some of those threatened multiple times.
U.S. Attorney David Hickton in Pittsburgh issued a statement Friday commending Pitt's response and confirming the threats "are being vigorously, aggressively and thoroughly investigated through every possible mean" by the region's Joint Terrorism Task Force, which includes the campus police and the FBI.