Via FoxNews.com:

Bomb units scrambled to investigate four suspicious devices reported almost simultaneously throughout Boston. The reports forced the temporary shutdown of a key inbound roadway and a bridge between Boston and Cambridge.

Boston Police say four calls, which all came in around 1 p.m., reported suspicious devices at the Boston University Bridge, the Longfellow Bridge, the corner of Stuart and Columbus Streets and at the Tufts-New England Medical Center.

The reports came just hours after authorities detonated a suspicious device at subway station located under Interstate 93 in Boston.
Subway service across the Longfellow Bridge, between Boston and Cambridge, was suspended temporarily.

“We’re taking this very seriously,” Boston Police Officer Eddie Chrispin said.

Update: A hoax.
Or something else.

Jason Smith e-mails: “Simultaneously placed at various strategic locations. I wonder if someone is sitting back and simply studying the emergency response protocol and timing… trying to identify weak spots and gaps to exploit for a real attack?”

Update II: Blame “Aqua Teen Hunger Force.”