The investigation continues into a weekend explosion at Harvard Medical School that authorities say was an intentional act. University police say an officer who responded to a fire alarm early Saturday morning encountered two people running from the Goldenson Building. The explosion occurred in a hallway on the fourth floor of the building, which houses labs and offices associated with the medical school’s Department of Neurobiology. No one was injured, there was no structural damage to the building and labs and equipment were untouched. The building has reopened, and an FBI spokesperson says the investigation remains “very active.”