Three suspicious packages have been found in the US, two addressed to a top Democrat and one to a former senior intelligence official, US media say.
Two items were found in a search of a Florida mail facility, addressed to Senator Cory Booker and ex-national intelligence director James Clapper.
A second item addressed to Mr Booker was found at a Manhattan post office.
The news came after several mail bombs were sent to prominent critics of US President Donald Trump.
The FBI has been searching the Florida facility for evidence. Figures like ex-President Barack Obama and actor Robert de Niro have already been targeted.
Security camera footage at the postal facility in Opa-locka, Miami, is being scrutinised. A bomb squad and canine unit had accompanied federal officials to the site, police from Miami-Dade County said.