CAMBRIDGE, Mass. — Students and staff at Harvard University were told to shelter in place and passengers on part of Boston’s subway system were rerouted to shuttle buses following reports Sunday of shots fired at a subway station near the school.

An alert sent to the Harvard community said the Massachusetts Bay Transit Authority, the Cambridge Police Department, Massachusetts State Police and Harvard University Police were searching the area near the Harvard Square station for a suspect. No injuries were immediately reported.

“Shelter in place. Please enter the nearest building and stay there until all clear is given,” the message said.

After delaying trains in the area, the MBTA announced it had decided to replace service there with shuttle buses due to “police activity.” Passengers were warned they could experience delays as the shuttles were being dispatched.