Emergency vehicles blared down Massachusetts Avenue for the better part of an hour late this morning, congregating at the Porter Square T station.

Police on the scene gave little information other than informing citizens that there had been “an accident.”

Word, however, trickled down the street that there was a body was under a train. Additional reports from bystanders were that a man had jumped in front of a Red Line train, but this has not confirmed by authorities.

When one bystander expressed his concern to a police officer about two T-related accidents in a week (referring to the Green Line accident near Government Center station on May 8), the officer told him, “This wasn’t that kind of accident.”

The MBTA has suspended service at Porter Square station while authorities investigate.

The MBTA posted this hastily-typed alert on its Web site:

Due to a medical emergency at Porter NB all train service will terminate at Harvard. As a result of the medical emergency, train service is experiencing service delays between Park Street and Harvard Station. Shuttle buses will provide service between Harvard (picking up at Johnson gate beside Church street enterance) and Alewife. 5/15/2009 11:012 AM

Police and emergency personnel were at the Porter Square station following an accident.

Police told T patrons the station would be closed while authorities investigate the scene.

Police directed traffic on Mass. Ave. The street was backed up for several blocks.

The MBTA provided buses for riders traveling between Harvard and Alewife stations.