According to university police, a campus officer responding to a fire alarm saw two unidentified individuals fleeing the building before reaching the source of the alert, media reports said.

The Boston Fire Department later determined that the explosion was deliberate.

A subsequent sweep of the building found no additional explosive devices, police said.

Images released by the authorities show the two suspects wearing face masks and possibly sweatshirts.

The FBI’s Boston Division is assisting Harvard University Police in the investigation, spokesperson Kristen Setera told CNN.

No details have been released about the suspects or the type of explosive device used.