Top Senate Republicans investigating the origins of the FBI’s Trump-Russia probe are pressing the bureau to produce all text messages belonging to former deputy director Andrew McCabe, calling the delay “unacceptable.”

In a letter to FBI Director Christopher Wray, Senate Homeland Security Committee Chairman Ron Johnson, R-Wis., and Senate Finance Committee Chairman Chuck Grassley, R-Iowa, demanded that the FBI turn over the documents, noting that their production would be responsive to a subpoena issued by Johnson’s committee in August.

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“As you know, on August 6, 2020, the Senate Homeland Security and Governmental Affairs Committee subpoenaed the FBI for all records related to the Crossfire Hurricane investigation, which requires that records actually be produced to the Committee, not merely made available for review in a reading room,” they wrote. “We have waited nearly 70 days to receive these text messages, and when records were actually produced, we received only 8 percent of what we know exists.”

They added: “It is simply unacceptable that we have waited so long to receive so little.”

Johnson and Grassley said the text messages belonging to McCabe that the FBI did produce “include notable information that is highly relevant to several aspects of the Committees’ oversight efforts.”

One aspect the committee is investigating involves records made public last week by Director of National Intelligence John Ratcliffe, who declassified documents that revealed former CIA Director John Brennan briefed former President Obama on Hillary Clinton’s purported “plan” to tie then-candidate Donald Trump to Russia as “a means of distracting the public form her use of a private email server” ahead of the 2016 presidential election.

The documents, which were first reported and exclusively obtained by Fox News, included Brennan’s handwritten notes — which were taken after he briefed Obama on the intelligence the CIA received — and a CIA memo, which revealed that officials referred the matter to former FBI Director James Comey and former FBI Special Agent Peter Strzok for potential investigative action.

"We have made a public commitment to determine and reveal the full extent of official investigative and intelligence action taken by federal officials against the Trump campaign, its presidential transition, and into the administration," the senators wrote, adding that the information that has already been made public "reveals what might be the most outrageous abuse of power in U.S. history against a presidential candidate and sitting president."

They added: "The American people deserve full transparency, and they have waited entirely too long—almost four years in some instances—for answers. In light of that history, it is astounding that the FBI can claim to need more time to identify and produce responsive records."

Johnson’s committee, in August, subpoenaed the FBI — their first subpoena as part of the committee’s probe into the origins of the Trump-Russia investigation.

The subpoena, obtained by Fox News, demanded that the FBI produce "all records related to the Crossfire Hurricane investigation."

"This includes, but is not limited to, all records provided or made available to the Inspector General of the U.S. Department of Justice for its review," the subpoena states, referring to DOJ Inspector General Michael Horowitz's review of abuses related to the Foreign Intelligence Surveillance Act (FISA).

The subpoena also demanded "all records related to requests" to the General Services Administration or the Office of the Inspector General for the GSA for "presidential transition records from November 2016 through December 2017."

"The FBI has already been producing documents and information to the Senate Homeland Security Committee, which are directly responsive to this subpoena," the FBI said in a statement to Fox News after receiving the subpoena. "As always, the FBI will continue to cooperate with the Committee's requests, consistent with our law enforcement and national security obligations."

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An FBI official told Fox News on Monday that the bureau has already been producing documents to the committee on a "rolling basis and have surged resources to do so.”

In June, the committee voted to authorize subpoenas to the FBI and other agencies for records and testimony from Obama-era officials related to the bureau's original Russia investigation and the Justice Department inspector general's review of that probe.

The committee authorized subpoenas to the FBI for the production of all records related to the Crossfire Hurricane investigation — the bureau's internal code name for the Russia probe, which began in July 2016.

The subpoenas would cover all records made available to DOJ Inspector General Michael Horowitz for his review of the Russia probe and alleged misconduct surrounding the Foreign Intelligence Surveillance Act (FISA) warrant approvals to surveil members of the Trump campaign.

The committee also authorized subpoenas to the State Department for the production of records related to meetings or communications between State Department officials or employees with ex-British Intelligence officer Christopher Steele, who compiled the now-infamous anti-Trump dossier which served as much of the basis for the FISA warrant applications to surveil former Trump campaign aide Carter Page. The subpoenas would cover documents from June 2016 through January 2017.

The committee also authorized subpoenas to the Office of the Director of National Intelligence for the production of all records related to the process of “unmasking” U.S. persons or entities affiliated "formally or informally" with the Trump campaign, the Trump transition team or the Trump administration from June 2015 through January 2017.

Johnson has the ability to issue subpoenas to a number of officials, including former FBI Counsel James Baker, Brennan, Comey, former Director of National Intelligence James Clapper, former Obama chief of staff Denis McDonough, former FBI lawyer Lisa Page, Strzok, Joe Pientka, former White House National Security Adviser Susan Rice, former FBI director of counterintelligence Bill Priestap, former U.N. Ambassador Samantha Power, Sidney Blumenthal, and a number of other Obama-era officials.

Also part of the committee’s probe is the process of “unmasking,” which occurs after U.S. citizens' conversations are incidentally picked up in conversations with foreign officials who are being monitored by the intelligence community. The U.S. citizens' identities are supposed to be protected if their participation is incidental and no wrongdoing is suspected. However, officials can determine the U.S. citizens' names through a process that is supposed to safeguard their rights.

In May, Johnson and Grassley made public a list of Obama officials who purportedly requested to “unmask” the identity of Michael Flynn, who at the time was President Trump’s incoming national security adviser.

Meanwhile, last week, upon the declassification of the Brennan notes and CIA memo to the FBI on the Clinton “plan,” President Trump, again, said he has “fully authorized the total Declassification of any & all documents" related to the Russia investigation and the FBI’s investigation into former Secretary of State Hillary Clinton’s use of a private email server.

“I have fully authorized the total Declassification of any & all documents pertaining to the single greatest political CRIME in American History, the Russia Hoax. Likewise, the Hillary Clinton Email Scandal. No redactions!” The president tweeted last week.

"All Russia Hoax Scandal information was Declassified by me long ago," Trump tweeted. "Unfortunately for our Country, people have acted very slowly, especially since it is perhaps the biggest political crime in the history of our Country.”

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He added: “Act!!!"

Last year, the president gave Attorney General Bill Barr authority to declassify any documents related to surveillance of the Trump campaign in 2016. Trump, at the time, also ordered members of the intelligence community to cooperate with Barr’s probe.

Allies of the president, including Republicans on Capitol Hill leading their own investigations into the origins of the Trump-Russia probe, have criticized officials like  Wray and CIA Director Gina Haspel, claiming that the directors have been blocking the release of documents.