BOSTON — Authorities are investigating a late-night blast at Harvard Medical School after what law-enforcement sources describe as an “explosive device” went off inside a campus building.

A Boston Police insider tells Mass Daily News there was a “possible explosion” overnight and that an “explosive device” is believed to have been intentionally set off. The source said a bomb unit swept the building and cleared it, with no further devices found.

Harvard University Police, Boston Police, and federal authorities responded to the scene, and the building was secured. No injuries have been reported.

Officials have not released details on what type of device was used or where in the building the blast occurred. Investigators have not publicly identified any suspects, and no motive has been confirmed.

The Harvard Crimson also reported the incident and said campus police notified students and staff after the device went off.

The investigation remains ongoing.

Check back with MDN for updates.