A report of shots fired at the Harvard Square MBTA station Sunday afternoon prompted a shelter in place as police searched for the suspect, according to a Harvard Alert sent by the university.

The MBTA reported police activity at the station and said the Red Line may experience delays. Shuttle buses also replaced service between the Central and Alewife stations.

Within an hour of the first alert, Harvard Alert announced that the search concluded and the shelter in place had been lifted at 3:19 p.m.

The Harvard Crimson reported that the station was blocked with caution tape but police were not stopping people from entering the station.

The MBTA, Massachusetts State Police, Cambridge Police Department and Harvard Media Relations did not immediately respond to requests for comment.

— This is a developing story.