Top GOP senator to FBI: 'Your disclosure is not fair to Congress, the American people' or Clinton
The Iowa Republican is requesting additional information from the FBI regarding the investigation.
Comey has faced criticism for making a statement about the investigation even though the FBI doesn't typically comment on ongoing investigations. He said in a letter to his employees that he felt an "obligation" to send a letter notifying Congress because he "testified repeatedly in recent months that our investigation was completed."
The Clinton campaign has also called on Comey to release more information on what the FBI has.
"Your letter indicated that the FBI learned in an 'unrelated case' of the existence of new emails pertinent to the Clinton inquiry and that you believed the FBI should take additional investigative steps to enable the new evidence to be reviewed," Grassley wrote in the letter.
"It is unclear from your letter what those additional investigative steps are, why they are necessary in order to review the emails, and whether they might include compulsory legal process dependent on the approval of prosecutors at the Department of Justice, such as seeking a search warrant."
The emails were uncovered after the FBI seized devices belonging to Huma Abedin and her husband, former congressman Anthony Weiner, reports said. Prosecutors issued a subpoena for Weiner's cellphone and other records in late September amid allegations that he had been sexting with a 15-year-old girl.
Critics are now accusing Comey of being motivated to influence the outcome of the election.
"You clearly faced a difficult decision about whether, what, and how much to disclose about this new information," Grassley wrote. "Any choice could be seen as affecting the election. Some critics of your decision to update your testimony to Congress are inexplicably calling on you with their next breath to release even more information. While I disagree with those who suggest you should have kept the FBI's discovery secret until after the election, I agree that your disclosure did not go far enough."
He continued: "Without additional context, your disclosure is not fair to Congress, the American people, or Secretary Clinton. The factual context is important."
Grassley also included a list of 10 questions he wants the FBI to answer about the investigation. He is requesting details about the time frame on the emails and whether they're new or are duplicates of emails the FBI has already recovered.
Grassley also questioned whether "political appointees at the Justice Department might be withholding approval for the FBI to seek search warrants and grand jury subpoenas."
"If the FBI is denied the ability to gather evidence through compulsory means, Secretary Clinton and her aides have enormous leverage to negotiate extraordinary concessions in exchange for voluntary cooperation," Grassley wrote. "This has already happened in the course of this investigation."