Former FBI agent Peter Strzok appeared to believe the CIA was leaking to the media about the Trump campaign and suspicious ties to the Russians and was involved in the investigation far earlier than previously known, according to text messages highlighted by a pair of Republican senators on Monday.

In a letter to intelligence community Inspector General Michael Atkinson, Sens. Ron Johnson, R-Wis., and Chuck Grassley, R-Iowa, quoted Strzok saying in December 2016 that “our sisters have begun leaking like mad. ... They’re kicking it into overdrive.” They note the watchdog is already looking into alleged Foreign Intelligence Surveillance Act abuse and urging him to look into these “apparent leaks” as well.

Johnson and Grassley point to what they believed was “the FBI’s apparent awareness of leaks by other agencies or entities to the media” by quoting a December 2016 text message from Strzok to former FBI lawyer Lisa Page discussing one of the FBI’s sister agencies, which said: “Think our sisters have begun leaking like mad. Scorned and worried and political, they’re kicking in to overdrive.”

The senators also point to an April 2017 email from Strzok to other colleagues at the FBI in which he seemed to complain about the CIA being involved in the Trump-Russia investigation earlier than he’d initially believed and about them not being fully transparent with the FBI. “I’m beginning to think the agency got info a lot earlier than we thought and hasn’t shared it completely with us,” Strzok said. “Might explain all these weird / seemingly incorrect leads all these media folks have. Would also highlight agency as source of some of the leaks.”

A news article that Strzok was specifically concerned about was an April 2017 piece in the Guardian titled “British spies were first to spot Trump team's links with Russia.” The article said, "Britain’s spy agencies played a crucial role in alerting their counterparts in Washington to contacts between members of Donald Trump’s campaign team and Russian intelligence operatives,” and that GCHQ, Britain’s leading intelligence agency, “first became aware in late 2015 of suspicious ‘interactions’ between figures connected to Trump and known or suspected Russian agents.” The article also said that “over the next six months, until summer 2016, a number of western agencies shared further information on contacts between Trump’s inner circle and Russians.” The Guardian report cites “a source close to UK intelligence,” which Strzok indicated was the CIA.

John Brennan, a vocal critic of Trump, was CIA director at the time. He reportedly pushed for British ex-spy Christopher Steele's unverified dossier on Trump's ties to Russia in an early version of the 2017 intelligence assessment on Russian interference, but he was then removed.

Special counsel Robert Mueller’s two-year investigation concluded that Russia interfered in the 2016 presidential election through social media disinformation campaigns and cyberattacks, but his investigation did not find sufficient evidence of criminal collusion between the Russians and the Trump campaign, or any other Americans.

Strzok and Page were engaged in an affair during the time they exchanged text messages. Strzok was an agent who had a leading role in the Clinton and Trump-Russia investigations; Page was an FBI lawyer. Mueller removed Strzok from the Russia investigation after the text messages came to light. Strzok was fired by the FBI, and Page also left the agency.

Johnson and Grassley said, “These texts and emails [from Strzok] raise a number of serious questions and concerns,” and they pressed the intelligence community inspector general to look for answers. The senators said they were “looking forward to the Justice Department Inspector General’s forthcoming reports reviewing potential FISA abuses and leaks from FBI personnel in order to gain a better understanding of what happened during the Russia investigation." They also said there needs to be an investigation into the broader intelligence community.

“These texts and emails demonstrate the need to investigate leaks from agencies or entities other than FBI,” Johnson and Grassley wrote. “Accordingly, has the Intelligence Community Office of the Inspector General initiated an investigation into these apparent leaks? If not, please explain why not.”

The letter comes amid increased calls from Republicans to “investigate the investigators.” Rep. Devin Nunes, R-Calif., has asked for the CIA, FBI, National Security Agency, and State Department to hand over investigative information about Maltese academic Joseph Mifsud, the man who told former Trump campaign adviser George Papadopoulos the Russians had "dirt" on Hillary Clinton. The Justice Department inspector general’s FISA abuse exploration is expected to wrap up in May or June. Attorney General William Barr has launched his own inquiry into the origins of the Trump-Russia investigation while saying that multiple criminal leak investigations are already underway.