In the midst of the ongoing US President Donald Trump's impeachment inquiry, the Department of Justice on Thursday has opened a criminal investigation into Russian intervention in Donald Trump's 2016 presidential campaign.

Attorney General William Barr's investigation into the Russian probe has evolved into a criminal inquiry by the Justice Department, sources were quoted as saying by the New York Times.

The move comes as Trump is facing impeachment for abuse of power after it was revealed last month that the US President had asserted pressure on Ukraine's President Volodymyr Zelensky to conduct an investigation into the former Vice President and 2020 candidate, Joe Biden and his son Hunter Biden.

Trump impeachment
US President Donald Trump.Reuters

While it is not known what are the potential crimes that were identified to open an investigation, it will be led by federal prosecutor John Durham who will be able to subpoena witness testimony and documents, convene a grand jury and file criminal charges. Reports suggest that while he has begun conducting interviews, some witnesses have declined to give their testimony, according to the CNN.

The probe will investigate the initial violations that led to special counsel Robert Mueller's inquiry into Russia's role in the 2016 presidential elections. Reports state that the probe emerged due to Barr's 'suspicions' that the officials who had overseen the Russian inquiry may have been involved in using illegal methods during the investigation.

"Deep State" spy operation

While some see the investigation as unusual as the Justice Department will be conducting an investigation into itself, some suggest that that move is a way to appease Trump of the claims he has made against the Russian probe over the years calling it a "witch hunt" and "deep state" spy operation.

With Trump firing FBI Director James B Comey, who was coordinating federal agents for the investigation of the Russian inquiry, and law enforcement and intelligence officials who had sought to block his elections, it is suggested that that Justice Department has become Trump's tool against dissent.

In a statement released by the Chairmen of the US House on Judiciary and Intelligence committees, Democratic Representative Jerrold Nadler and Adam Schiff the reports "raise profound new concerns and indicate the Justice Department "has lost its independence and become a vehicle for President Trump's political revenge."

"If the Department of Justice may be used as a tool of political retribution, or to help the President with a political narrative for the next election, the rule of law will suffer new and irreparable damage," the statement read.

The inquiry is likely to favour Trump's earlier allegations that the FBI officials, who were involved in opening the counterintelligence investigation into Moscow's intervention into his campaign, had committed treason. Calling the inquiry as to the biggest political scandal in US history, in an interview with Fox News in May, Trump said, "We can never allow these treasonous acts to happen to another president."