An explosion inside a Harvard University medical building early Saturday morning appears to have been “intentional,” police said.

A Harvard University Police Department officer arrived at the Goldenson Building after a fire alarm went off at 2:48 a.m., Harvard police said in a statement.

While responding to the call, the officer noted that he saw two “unidentified individuals fleeing from the building,” according to the statement. The officer “attempted to stop the individuals,” but was unsuccessful.

The explosion occurred on the building’s fourth floor, and an arson team assessed that the explosion “appeared to be intentional.”

The government shutdown puts millions at risk of losing food assistance — and Trump and lawmakers are MIA. We're covering the devastating consequences of the government's inaction. Support the journalism that holds our leaders to account.