Justice Department review of Russian Federation probe is now a criminal probe

The person, who spoke to Reuters on condition of anonymity, declined to say whether a grand jury had been convened in the investigation.

It was not clear what potential crime Mr. Durham is investigating, nor when the criminal investigation was prompted. Durham has been examining whether the government's intelligence collection efforts related to Trump associates were lawful and appropriate, both during the 2016 presidential campaign and after President Trump was inaugurated.

However, the report - based on almost two years of interviews by Mueller's team with Trump's inner circle - emphasised that, contrary to the Republican president's claim, he was not cleared of obstruction of justice.

This comes after Special Counsel Robert Mueller III closed the official investigation months ago. Mueller also examined 10 possible instances of obstruction of justice and has pointedly said he could not exonerate the president.

The criminal investigation into how the sprawling Russian Federation probe began will be headed by prosecutor John Durham, who will have subpoena power over testimony and documents, the New York Times reported.

The Department Justice is opening a criminal investigation into its own Russian Federation probe.

As part of his inquiry, Barr has asked Australian and British justice officials for assistance and visited Italy twice, meeting intelligence agents in Rome in August and September to learn more about people mentioned in Mueller's report.

The White House did not immediately respond to a request for comment Thursday.