Members of U.S. Congress, have called for the appointment of a special prosecutor to investigate a possible Trump campaign ties to Russian’s meddling in the 2016 U.S. presidential elections following the sack of FBI Director James Comey, a lead investigator of the matter.

It means Trump could lose hold of the investigation if a special prosecutor is appointed.

Some of the senators equated the firing with events known as the “Saturday Night Massacre” during the Watergate scandal that brought down President Richard Nixon.

Senate Minority Leader Charles Schumer, D-N.Y., said he told Trump that he had made a “big mistake” when informed of the decision.

Schumer wondered aloud whether the firing meant Comey’s investigation was “getting too close to home,” and he said the handling of a credible investigation depends on Deputy Attorney General Rod J. Rosenstein naming a “fearless, independent” special prosecutor.

“Mr. Rosenstein, America depends on you to restore faith in our criminal justice system which is going to be badly shattered after the administration’s actions,” Schumer said.

Republican Sen. John McCain of Arizona called for the creation of a special congressional committee on Russia, while Republican Rep. Justin Amash of Michigan said he and his staff were “reviewing legislation to establish an independent commission on Russia.”

“James Comey is a man of honour and integrity, and he has led the FBI well in extraordinary circumstances,” McCain said.

Comey, a Republican who had served in the George W. Bush administration as second in command in the Justice Department was the surprise choice of President Barack Obama for the FBI post.

He had established his independence in March 2004 when then-White House counsel Alberto Gonzales sought to get Comey’s boss, Attorney General John Ashcroft, to sign off on a secret National Security Agency wiretap program.

Ashcroft, seriously ill in the hospital with pancreatitis, had turned his duties over to Comey, who told Gonzales in Ashcroft’s hospital room that he refused to authorise the program.

Rep. Adam Schiff of California, the top Democrat on the troubled House intelligence committee, said the firing raised profound questions about White House interference in a criminal probe.

Senate Minority Whip Dick Durbin, D-Ill., suggested Trump’s action poses serious constitutional issues, while others called the development “Nixonian.”

“The termination and removal of James Comey as director of the Federal Bureau of Investigation raises the critical question as to whether the FBI investigation of Russian interference in the last presidential campaign will continue,” Durbin said.