Boston manhunt for bomb suspect Dzhokhar Tsarnaev

The Guardian's Adam Gabbatt is in Watertown, Massachusetts, the site of a major law enforcement response which has been unfolding in the last few hours to an unknown incident. 

Adam reports: More than 20 police and emergency vehicles have left the cordoned-off area of Watertown in the last few minutes. I am stationed around two blocks away from the home that was apparently the focus of police attention. A nearby is lined with scores of police cars for more than a mile on either side of the blocked-off area. Within the police area there are still authorities in SWAT gear. A police helicopter is continuing to circle overhead. As I write, an ATF fire and explosives vehicle has pulled into the cordoned off police zone. It is not clear what, if anything, the vehicle is being used for.

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