Senate Judiciary Committee Chairman Chuck Grassley (R-Iowa) and Senate Homeland Security Committee Chairman Ron Johnson Ronald (Ron) Harold Johnson CIA found Putin 'probably directing' campaign against Biden: report This week: Supreme Court fight over Ginsburg's seat upends Congress's agenda GOP set to release controversial Biden report MORE (R-Wis.) are asking the FBI to brief them on its probe of Democratic presidential nominee Hillary Clinton’s handling of classified information on a private email server.

The revelation Friday that the FBI was looking into new information in the Clinton case came as a shock to Washington — and to Grassley and Johnson.

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“The letter from Director Comey was unsolicited and, quite honestly, surprising. But it's left a lot more questions than answers for both the FBI and Secretary Clinton,” Grassley said in a statement.

“Congress and the public deserve more context to properly assess what evidence the FBI has discovered and what it plans to do with it. I've asked for a briefing from the FBI as soon as possible,” he said.

FBI Director James Comey wrote to eight Senate and House committee chairmen Friday informing them that he instructed his investigators to review new evidence in connection with the previously completed Clinton case.

“In connection with an unrelated case, the FBI has learned of the existence of emails that appear to be pertinent to this investigation,” Comey wrote.

After receiving a briefing from his investigative team, he agreed “to allow investigators to review these emails to determine whether they contain classified information.”

Senate Intelligence Committee Chairman Richard Burr Richard Mauze BurrRep. Mark Walker says he's been contacted about Liberty University vacancy Overnight Defense: Trump rejects major cut to military health care | Senate report says Trump campaign's Russia contacts posed 'grave' threat Senate report describes closer ties between 2016 Trump campaign, Russia MORE (R-N.C) and Senate Homeland Security Committee Chairman Ron Johnson (R-Wis.) also received the letter, as did Sen. Richard Shelby (R-Ala.), the chairman of the Appropriations Subcommittee on Commerce, Justice, Science and Related Agencies.

A Republican source familiar with the letter said it popped up in staffers’ email inboxes Friday morning with little warning.

Grassley has criticized the FBI’s handling of its probe. In September, he blasted the agency for not releasing the unclassified emails it reviewed in its investigation of Clinton.

In July, Grassley called Comey’s decision not to recommend Clinton’s prosecution “suspect” and suggested possible conflicts of interest.

“Prosecutorial decisions made under the shadow of apparent conflicts of interest are understandably suspect,” he said, alluding to a 30-minute private meeting former President Bill Clinton William (Bill) Jefferson ClintonChelsea Clinton: Trump isn't building public confidence in a vaccine Hillary Clinton launching podcast this month GOP brushes back charges of hypocrisy in Supreme Court fight MORE held with Attorney General Loretta Lynch on an airport tarmac earlier in the summer.

Johnson said in a statement the FBI should be fully forthcoming with Congress about whatever new evidence it discovered in connection to Clinton.

“I hope that the FBI will be transparent with Congress and the American people as it continues to examine Secretary Clinton’s extremely careless behavior,” he said.

He called the FBI’s announcement “an important step toward accountability.”

This story was updated at 4:28 p.m.