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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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Police officer shot dead on MIT campus near Boston

A police officer for the Massachusetts Institute of Technology has been shot dead at the US university's campus in Cambridge near Boston.

The death was confirmed by authorities, who said no suspects were in custody.

Police and the FBI responded to gunshots heard at Building 32 on the campus. Students have been told to stay indoors and away from the area.

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