Sen. Tim Kaine (D-Va.) suggested Saturday that some officials at the FBI are “actively working” to support Republican presidential candidate Donald Trump.

Kaine, the Democratic vice-presidential candidate, made the claim during an interview with Fusion, a Miami-based television network targeting bicultural millennials. The comments mark an escalation in the Clinton campaign's response to the FBI's renewed inquiry into Hillary Clinton's use of a private email server when she served as secretary of state.

Kaine called the FBI a “leaky sieve” and accused Director James B. Comey of breaking agency protocol by discussing a politically sensitive case so close to an election. He also dismissed former New York mayor Rudolph W. Giuliani’s decision to back off claims that he, Giuliani, had been given advance notice of the FBI's plans to possibly reopen the Clinton investigation.

“I don’t think Giuliani’s walk-back is credible,” Kaine said. “I think the FBI sadly has become like a leaky sieve.”

Giuliani, a prominent Trump supporter, told Fox News in the days before Comey alerted lawmakers to the FBI's renewed inquiry that there would be a “big surprise” coming from the agency. Asked about his claims again on Friday, Giuliani said on Fox's “Fox and Friends” program, “You’re darn right I heard something.” But Giuliani pulled back on Saturday, saying he was aware only of “tremendous anger” among former FBI agents at Comey.

Comey's decision to alert Congress about his review of the Clinton case “suggests that it’s probably more likely explained that [Comey] knew that the FBI is not only a leaky sieve but there were people within the FBI actively working — actively working — to try to help the Trump campaign,” Kaine said. “This is just absolutely staggering, and it is a massive blow to the integrity of [the FBI].”

Kaine added that he thinks Comey was under pressure to release information to Congress because “subordinates would do it if he didn’t.”

The FBI decided to review the Clinton case after discovering new emails potentially relevant to the original investigation. Senior FBI officials were informed about the discovery of new emails, obtained in relation to an investigation of former congressman Anthony Weiner (D-N.Y.), at least two weeks before Comey notified Congress, federal officials familiar with the investigation have told The Washington Post.

The officials said that Comey was told that there were new emails before he received a formal briefing and opted to inform lawmakers.

The Clinton campaign has publicly questioned Comey's motives in making the announcement as well as his fitness to serve — despite praising his leadership of the FBI after he announced in July that the agency would not recommend the email case for prosecution. Clinton herself has raised the issue on the stump, while top aides and surrogates have called Comey's judgment into question.

Kaine was campaigning Saturday in Florida when he made his remarks to Fusion. He is expected to maintain a breakneck pace in the closing hours of the campaign, including an appearance Sunday on CBS's “Face the Nation” — where he is likely to be asked to clarify the comments he made to Fusion — and a visit to Wisconsin. On Monday, he will campaign in his home state of Virginia, as well as in Pennsylvania and North Carolina.