Authorities found two more suspicious packages on Friday addressed to U.S. Senator Cory Booker and James Clapper, the former U.S. director of national intelligence.
The discoveries come during a manhunt for the person who sent bombs to prominent Democrats and critics of US President Donald Trump.
The 11th package was found at a mail sorting facility in Opa-Locka, near Miami, and was addressed to Booker, the Democratic senator from New Jersey, the FBI said on Twitter. A 12th package was addressed to James Clapper, the former director of national intelligence, and sent to CNN, the cable network reported.
Police are on the scene in midtown Manhattan.
Meanwhile, a local police bomb squad and canine units joined federal investigators on Thursday to examine a sprawling U.S. mail distribution centre at Opa-Locka, northwest of Miami, Miami-Dade County police said.
U.S. Homeland Security Secretary Kirstjen Nielsen said that Florida appeared to be the starting point for at least some of the bomb shipments.