Pipe bombs targeting prominent Democrats and President Trump's biggest foes have been discovered across the U.S. with law enforcement suspecting a serial bomber is behind the rash of homemade explosives sent in the mail.

Secret Service agents revealed on Wednesday they had intercepted two explosives en route to former President Obama's Washington D.C. home and Hillary and Bill Clinton's property in Chappaqua, New York.

A short time later, a police bomb squad was sent to CNN's offices in New York City and the newsroom was evacuated because of a pipe bomb found in an envelope addressed to former CIA director John Brennan.