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Updated November 1, 2025, at 6:21 p.m.

A device exploded inside the Goldenson Building in Harvard’s Longwood medical campus early Saturday morning, according to a message from the Harvard University Police Department to University affiliates.

The Boston Fire Department Arson Unit responded to the incident and determined the explosion to be intentional.

The explosion took place on an area of the fourth floor of Goldenson, a Harvard Medical School building on the school’s main quad. An officer who responded shortly before 3 a.m. observed two individuals fleeing the building, according to the email sent by HUPD spokesperson Steven G. Catalano this afternoon.

HUPD sent a subsequent email to Harvard affiliates shortly after 5 p.m. asking for assistance identifying two men, who they described as suspects. The images were captured on security footage.

Both men are shown wearing sweatshirts with hoods and ski masks.

The Boston Police Department performed a sweep of the building and determined there were no additional devices in the building. No injuries were reported in relation to the incident.

HMS administrators confirmed that the building “has been cleared and remains open,” except for the fourth floor, according to an email obtained by The Crimson sent to HMS staff based in Goldenson. The email, sent at roughly 6 p.m., did not name which labs or offices were affected.

HMS employees in the building were also instructed to stay away from campus until Monday unless necessary.

“If you had not intended to or do not need to come to campus this weekend, you should not come in,” the email read.

Catalano declined to comment beyond HUPD’s emailed statements. A BPD spokesperson declined to comment on the incident. A spokesperson for the Boston Fire Department could not immediately be reached for comment.

HUPD is actively investigating the incident with local, state, and federal authorities. The FBI was on scene Saturday afternoon assisting HUPD, according to FBI spokesperson Kristen M. Setera.

This is a developing story and will be updated.

—Staff writer Matan H. Josephy can be reached at matan.josephy@thecrimson.com. Follow him on X @matanjosephy.

—Staff writer Laurel M. Shugart can be reached at laurel.shugart@thecrimson.com. Follow them on X @laurelmshugart.