US President Donald Trump has been briefed on the latest suspicious packages found on Thursday, White House spokeswoman Sarah Sanders said.
The packages were addressed to former US Vice President Joe Biden and to actor Robert De Niro.
Sanders, speaking in an interview on Fox News, said the White House continued to condemn any attempted violence and would continue to direct federal resources toward the ongoing investigation.
The wave of suspected bombs targeted well-known Democratic Party figures and critics of Trump as a manhunt intensified for a serial bomber less than two weeks before congressional elections on Nov. 6.
None of the nine devices went off and no injuries were reported, but some top Democrats called the threats a symptom of a coarsening brand of political rhetoric promoted by Trump, who also condemned the acts.