The three people arrested in connection with the Boston Marathon bombings have been under FBI surveillance for around 10 days and are likely to have taken items out of Dzohkhar Tsarnaev's dormitory, according to NBC.
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The singer had been tweeting in support of migrants when she was bombarded with abusive messages.
Ministers are reportedly considering plans in a bid to lower inward migration.
In a tweet on Saturday, the US president didn't give a reason for his absence but said he wished"everyone well and have a great evening".