PITTSBURGH — Pittsburgh police and federal prosecutors won’t say why campus and city police have been guarding the home of Carnegie Mellon University’s president for about a week.

A Pittsburgh newspaper reports a spokeswoman for the U.S. Postal Inspector confirmed a related investigation at the university, but wouldn’t provide details.

The postal inspector’s office handles mail-related crimes, including threats communicated that way, but spokesmen for the Pittsburgh police and U.S. Attorney’s Office won’t comment on the police presence or the acknowledgement of an investigation involving the postal inspector’s office.

University officials also are not commenting on the police presence near the university-owned home of president Jared Cohon.

The 65-year-old Cohon has headed the university since 1997 but has previously announced plans to retire in June. A committee is searching for his replacement.