(CNN) The Ukraine allegations that President Donald Trump's personal attorney Rudy Giuliani is providing to the Justice Department are being vetted by investigators in the US Attorney's Office in Pittsburgh, two US law enforcement officials said.

The officials told CNN that the Pittsburgh office has expertise on Russia and its cyber operations, including the 2016 disinformation campaign the Russians carried out.

A spokeswoman for the US attorney's office in Pittsburgh declined to comment.

On Monday, Attorney General William Barr confirmed that the Justice Department has been receiving information from Giuliani about his operation in Ukraine, where Giuliani has been seeking dirt on former Vice President Joe Biden and his son Hunter Biden. The attorney general said the Justice Department has an "obligation to have an open door to anybody who wishes to provide us information that they think is relevant" but expressed skepticism about the reporting, noting that Ukraine can be a dubious source.

Barr said the Justice Department has put in place special precautions to ensure that Giuliani's information is "carefully scrutinized."

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