Rudolph Giuliani, attorney for President Donald Trump, arrives for a press conference in the Republican National Committee on complaints regarding the result of the 2020 presidential election on Thursday, November 19, 2020.

Tom Williams | CQ Appeal, Inc. | Getty Images

Federal investigators on Wednesday carried out a search warrant on the Manhattan apartment of Rudy Giuliani, former New York City mayor who was former President Donald Trump’s personal attorney.

The search was part of a criminal investigation into Giuliani’s business in Ukraine, the New York Times reported on Wednesday, citing three people with knowledge of the matter.

The New York prosecutor’s office last year obtained approval from top Justice Department officials to request a search warrant for Giuliani’s electronic communications, NBC reported. Giuliani is the former United States attorney for the Southern District of New York, the same bureau that investigates him.

A Giuliani attorney, Robert Costello, said authorities arrived at the Upper East Side apartment at 6 a.m. and confiscated electronic devices during the search, the Wall Street Journal reported. The investigation is investigating possible violations of foreign lobbying rules, and the search warrant looked for communication between Giuliani and others, including Conservative columnist John Solomon, Costello told the journal.

Giuliani, Costello and a Trump spokesman did not immediately respond to CNBC’s requests for comment on the report. A spokesman for the US Attorney’s Office for the Southern District of New York declined to speak to CNBC about the reported raid on Giuliani’s home.

The Justice Department did not immediately comment.

In 2019, Giuliani attempted to gather harmful information about President Joe Biden’s son, Hunter Biden, in connection with J├Ąger’s business dealings in Ukraine.

Efforts by Giuliani, Trump, and others in his orbit to pressure Ukrainian officials to investigate the Bidens – or at least announce an investigation – prompted House Democrats to indict the former president for the first time. Democrats argued that Trump’s re-election ambitions sparked the dirt-seeking efforts.

The Senate, which was held by Republicans at the time, acquitted Trump.

Prosecutors in Manhattan were known to be reviewing Giuliani’s bank records in connection with an investigation into his activities in Ukraine.

Giuliani responded to the investigation last winter, claiming in an angry tweet that federal investigators were acting as “secret police” to aid Biden.

“You want to confiscate my e-mails. No reason. No wrongdoing. Attorney-client privilege.?” Giuliani tweeted on December 22nd.

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– CNBC’s Amanda Macias and Dan Mangan contributed to this report.