TEHRAN - Rob Malley, the U.S. special envoy on Iran, has been placed on leave without pay, which occurred after his security clearance was suspended earlier this year amid an investigation into his handling of classified material, multiple sources told CNN.

A U.S. official said that Malley’s clearance was suspended amid a State Department diplomatic security investigation into the possible mishandling of classified information. Another source familiar with the matter said he was placed on unpaid leave on Thursday afternoon.

“I have been informed that my security clearance is under review. I have not been provided any further information, but I expect the investigation to be resolved favorably and soon. In the meantime, I am on leave,” Malley told CNN.

For a period of time following the State Department investigation, Malley remained on the job but was not allowed to access classified information, said the U.S. official, who requested anonymity while discussing a sensitive matter.

Two sources familiar with the matter confirmed the State Department investigation identified an issue with Malley’s security clearance.

State Department spokesperson Matt Miller confirmed to CNN on Thursday afternoon that Malley was on leave, though earlier in the day he said that Malley was still the special envoy for Iran.

“Rob Malley is on leave and Abram Paley is serving as acting Special Envoy for Iran and leading the Department’s work in this area,” Miller told CNN on Thursday afternoon, after earlier in the day saying that Malley remained in the role.

Previously, Malley had played a key role in U.S. efforts to revive the Iran nuclear deal, one of the thorniest foreign policy challenges facing the Biden administration following former President Donald Trump’s decision to walk away from the agreement that Malley played an important role in negotiating under President Barack Obama. He had also played a leading role in seeking to secure the release of Americans detained in Iran.

Earlier this year, two sources said, the State Department ramped up its own investigation into Malley’s handling of classified information, which led to his clearance being suspended within the last two months.

It’s not clear what was uncovered that specifically led to Malley’s clearance being suspended. The sources did not have any indication there was a criminal probe related to the matter.

The move to suspend Malley’s security clearance was not communicated widely within the State Department or across the Biden administration, as the department kept him in his role and made no official announcements about replacing him. Some officials at the State Department were told that Malley was handing personal matters, which is why he had taken a back seat on the Iran portfolio, two State Department officials and a third person who was briefed told CNN.

In recent months, Malley has appeared to maintain a prominent role in working to secure the release of Americans detained in Iran. He has been in regular contact with the families of those held, speaking with them as recently as within the last week, two sources told CNN.

Malley also engaged with the Iranian ambassador to the United Nations earlier this year, but it is unclear if those engagements came before or after his clearance was suspended.

But Malley has been sidelined from the crucial effort to put constraints on Iran’s nuclear program and the Biden administration has put Brett McGurk, a top National Security Council official, into that role.

Malley, who was appointed as special envoy for Iran about a week after Joe Biden took office in 2021, engaged in the efforts to revive the Iran nuclear deal since the beginning of the Biden administration. But the intense efforts – which included Malley shuttling to and from the Middle East and largely working through U.S. allies to communicate with Iran – did not produce any breakthroughs.

By the end of 2022 State Department officials were saying that efforts to revive the deal were not the department’s focus.

Malley worked on the Iran portfolio during the Clinton and Obama administrations. Under Obama he was part of the diplomatic negotiating team that helped craft the Iran nuclear deal. He has been a target for Iran hawks who cast him as an Iran sympathizer.

Malley also has been friends with Secretary of State Antony Blinken for decades, dating back to their days as teenage classmates in Paris.