Federal agents on Wednesday searched Rudolph Giuliani's Manhattan apartment and office, escalating their investigation into the Ukrainian business dealings of the onetime personal lawyer of former President Donald Trump.

A lawyer for Giuliani, 76, confirmed that search warrants had been executed, and that authorities had seized cell phones. The warrants included an allegation that Giuliani failed to register as a foreign agent, a violation of lobbying laws.

Prior to the 2020 presidential election, Giuliani led an effort to dig up dirt on then-Democratic contender Joe Biden and his son Hunter in Ukraine.