CNN and USA Today filed lawsuits Thursday ordering the Federal Bureau of Investigation to hand over James Comey's memos which detailed private meetings he had with President Donald Trump, according to The Hill.
Trump has not been shy about venting his frustration on Twitter.
He appeared to be referring to Rod Rosenstein, deputy attorney general who is now leading the probe.
U.S. Deputy Attorney General Rod Rosenstein has privately acknowledged he may need to recuse himself from matters relating to the probe into Russian Federation and last year's U.S. election, given that he could become a potential witness in the investigation, ABC News reported on Friday, citing unnamed sources.
He was also involved into the Iran-Contra and the Watergate investigations.
Trump's tweet could force Rosenstein's recusal in the Mueller investigation, according to a Bloomberg View article by Harvard law professor Noah Feldman.
Gingrich, who worked as a strategist for Trump and appears as his surrogate on television, argued on Twitter earlier this week that "Republicans are delusional if they think the special counsel is going to be fair".
WASHINGTON (AP) - A member of the president's outside legal team said Sunday that Donald Trump is not under investigation, days after Trump tweeted about being the target of a "witch hunt". Comey's firing likely will be part of that probe.
"If he fires Mueller, I will tell you, we are right on the brink of a constitutional crisis", the IL senator said.
The newspaper said the information came from officials who spoke on condition of anonymity because they were not authorized to speak publicly.
The Republican president has repeatedly complained about the probe, calling it a witch hunt and saying Democrats can not accept his election victory.
The letter said the investigation will also probe Comey's testimony that Loretta Lynch, as President Barack Obama's attorney general, had directed him to describe an FBI probe into Hillary Clinton's email practices as merely a "matter" and to avoid calling it an investigation.
Even though Mueller is technically leading the investigation, the DOJ controls the funding for the investigation and can fire Mueller if the department decides it's warranted.
Inside the White House, a sense of foreboding has taken hold on even the most junior staff and up to the Oval Office, as news emerged that Vice President Mike Pence has hired a high-powered outside counsel to represent him. The transition, a nonprofit structurally separate from the Trump campaign, continues to operate with a small staff. The memo asks for preservation of electronic communications and data, telephone logs, audio recordings, videos, calendars and other items.
And as Rep. Ted Lieu (D-Calif.) declared in a tweet Thursday, "If Trump fired Mueller (he'd also have to fire Dep AG Rosenstein), it would be an 11 on the Richter scale of #obstructionofjustice".
USA intelligence agencies concluded in January that Russian Federation interfered in the presidential race to try to help Trump win, in part by hacking and releasing emails damaging to his Democratic opponent, Hillary Clinton.