Federal, state and local authorities have been searching the woods near the University of Massachusetts' Dartmouth campus as part of their investigation into the Boston Marathon bombing.
A spokeswoman for US attorney Carmen Ortiz said the US Bureau of Alcohol, Tobacco, Firearms and Explosives is taking the lead on the search and said there was no threat to public safety.
Suspect Dzhokhar Tsarnaev, who is recovering in a prison hospital after being wounded in a shootout with police, was a student at UMass-Dartmouth.
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There is no evidence the Westminster attacker Khalid Masood was associated with so-called Islamic State or al Qaeda, the Met Police said.
Janet Ajao said in a statement: "I do not condone his actions nor support the beliefs he held that led to him committing this atrocity."
After the PM triggers Article 50, Britain will need the other EU nations to agree to deals. Gibraltar could be key to Spain's demands.