(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."
But Democrats have decried the Justice Department's arrangement with Giuliani, questioning the situation over Barr's connection to the President's own dealings in Ukraine and the fact that two Giuliani associates who worked in Ukraine, Igor Fruman and Lev Parnas, were indicted on campaign finance charges last year.
The Justice Department's process for Giuliani to provide Ukraine information is one of several DOJ actions facing scrutiny for political influence involving the President. On Tuesday, Justice Department officials said they were backing away from the request that Trump confidante Roger Stone receive up to nine years in prison, just hours after Trump tweeted attacking the sentencing recommendation from prosecutors from the US Attorney's office in Washington.
Sen. Richard Blumenthal, a Connecticut Democrat, called Giuliani's line into the Justice Department "chilling" and "extraordinary dangerous."
"This kind of back channel for the President's personal attorney, a political operative ought to ... deeply alarm and frighten America because it in essence, weaponizes law enforcement and the Department of Justice as a political tool," Blumenthal said.
Sen. Dick Durbin of Illinois, the No. 2 Senate Democrat, said he hoped that "sober minds" at the Justice Department would keep the arrangement from getting carried away.
"I would like to believe that Giuliani is just another American citizen with information important to the Department of Justice, but I know better," Durbin said. "He's an insider in the Trump administration and he has an open forum when it comes to the Attorney General, Bill Barr, to take a look at his so-called evidence."
House Judiciary Chairman Jerry Nadler on Monday sent Barr a letter demanding answers to a series of questions related to Giuliani, calling it a "significant departure" from traditional channels for receiving information.
Republicans, however, downplayed any concerns about Giuliani's efforts with DOJ, which were publicly disclosed on Sunday by GOP Sen. Lindsey Graham of South Carolina, who said that any documents coming from Ukraine should be turned over to US intelligence agencies.
Sen. Josh Hawley, a Missouri Republican, said he wasn't familiar with the details of what Giuliani was providing, but said that anyone with relevant information should provide information to law enforcement officials.
"As a former prosecutor, we get tips all the time, that's fine," Hawley said.
Senate Finance Chairman Chuck Grassley of Iowa and Homeland Security Chairman Ron Johnson of Wisconsin are conducting their own investigation into the Bidens and Burisma, the energy company that hired Hunter Biden. Last week, the Republican chairmen wrote to the Secret Service seeking Hunter Biden's travel records.
Giuliani has long been touting allegations stemming from his investigation into the work that Joe and Hunter Biden did related to Burisma. Trump and his allies have made unfounded and false claims to allege that the Bidens acted corruptly in Ukraine.
The allegations played a prominent role during the President's Senate impeachment trial. Trump's lawyers argued he had legitimate reasons to worry about corruption involving the Bidens and Ukraine after Joe Biden pushed for the firing of Ukrainian prosecutor general Viktor Shokin. But multiple witnesses testified that Biden's actions in Ukraine were consistent with official US government policy, backed by European allies as well as both Republicans and Democrats in Congress.