Donald Trump has been accused of using the US Justice Department as a political tool after the department turned its review of the origins of the Russia Investigation into a criminal inquiry.
The US president has previously floated unproven theories that his predecessor Barack Obama's officials were acting on political motivations when they launched the investigation before the 2016 election, fuelled with help from allies like Britain.
The Russia Investigation, as it came to be known, was set up before the 2016 election to look into potential collusion between the Trump campaign and Russia. The investigation led to several senior Trump campaign figures being convicted.
A review into the origins of the Russia Investigation was launched in May by William Barr, the US Attorney General.
It is being overseen by Mr Barr and run by John Durham, a US attorney in Connecticut, to look into whether the US intelligence gathering that sparked the Russia investigation was lawful and appropriate.
Earlier this month, The Telegraph revealed that Mr Barr met with Priti Patel, the Home Secretary, in London this summer as he sought British help in the investigation. Mr Barr has also asked Australia and Italy to cooperate with the probe.
It has now emerged that the review has been turned into a criminal probe - meaning the US Justice Department is now criminally investigating itself.
The development, first reported by the New York Times, may indicate that Mr Durham has found evidence of wrongdoing.
The significance of it becoming a criminal investigation is that it gives Mr Durham the authority to convene a grand jury to assess evidence and compel testimony from witnesses - a process commonly used before criminal charges are filed in the US legal system.
However, it is unclear what specific crimes may be under investigation, or who would be charged.
The development has prompted criticism from several Democrats, who claim that Mr Trump is using the investigation as a mechanism to punish his political enemies.
Two of the Democrats leading an impeachment inquiry into Mr Trump, Jerry Nadler and Adam Schiff, issued a joint statement saying they the reports raised profound concerns that "the Department of Justice under AG Barr has lost its independence and become a vehicle for President Trump's political revenge".
Mr Trump praised the criminal investigation on Friday, saying: "Investigate the investigators" before citing James Comey, the former FBI director, and the former director of National Intelligence, James Clapper.
"As you know there's been a long term look-at, and it looks like it's being very serious from what I'm hearing," he said. He went on to say: "I can't tell you what's happening, I will tell you this: I think you're going to see a lot of very bad things."
However he the president suggested he was not personally involved in the direction of the probe, saying he would "leave it all up to the attorney general."
At the time the Justice Department's independent watchdog was already conducting a similar investigation. That investigation has already been completed and is expected to be released publicly very soon.