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.
More top news
President Donald Trump has requested that the Justice Department investigates whether the FBI infiltrated his campaign.
High pressure will help keep conditions relatively quiet through the course of this week.
Police are subject to the same road laws as civilians, meaning they can be prosecuted if something goes wrong when pursuing motorists.