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Boston bombs 'remote trigger'

US investigators have revealed the two bombs that went off at the Boston Marathon were detonated with the kind of remote control device used for a toy car.

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In pictures: Police search house to house for suspect

Police are searching house to house in Watertown, Massachusetts, for the Boston Marathon bombing suspect still on the run.

The neighbourhood of Watertown, Massachusetts, is on lockdown. Credit: REUTERS/Brian Snyder
A resident watches as police officers search houses for Dzhokhar Tsarnaev. Credit: REUTERS/Brian Snyder
Police officers continued a house to house search for the suspect still at large. Credit: REUTERS/Brian Snyder

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