The usual Saturday morning bustle of Harvard Square was disrupted when Cambridge Police and the Cambridge bomb squad swarmed the area in response to a bomb threat.

Police closed down Massachusetts Avenue, the Harvard Square MBTA stop, and several nearby Square businesses.

“Where the T stop was, there must have been like eight or 10 SWAT cars and a big squad car parked there,” said Pierce E. Tria ’10. Tria said he saw Harvard and Cambridge police officers cordoning off Holyoke and Mount Auburn Streets.

The scare was precipitated by a call to Cambridge police made by a pedestrian early Saturday morning, according to Nick Nicholas, an employee of the Crimson Corner newsstand. The pedestrian heard a ticking noise coming from the two mailboxes outside of the Harvard Square Bank of America, Nicholas said, and the source of the ticking was later discovered to be a “clicker” placed in one of the mailboxes.

A “clicker” is an electronic device often used in restaurants to alert patrons when their table is ready, another Square employee said.

The Cambridge Police Department could not be reached for comment over the weekend.

The Harvard Square Finagle A Bagel, CVS, Sovereign Bank and Bank of America were all closed from approximately 9 a.m. to 11 a.m., according to Reda Bichri, an employee of The Body Shop. The Harvard Coop and Crimson Corner News Stand also closed for this timeframe, Nicholas said.

Red line trains bypassed the Harvard Square station for those two hours, a transit worker said, and all Harvard Yard gates along Mass. Ave from Johnston Gate to the Widener gate were also closed, according to Harvard security personnel.

The last bomb scare to threaten University property occurred in February 2000, when a phoned-in bomb threat and reports of a suspicious smell caused the evacuation of two Harvard Extension School buildings.

—Staff writer Emily J. Hogan can be reached at ejhogan@fas.harvard.edu.