Rob Malley, the US 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 US 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

Texas Republican Rep. Michael McCaul wrote a letter on Friday to Secretary of State Antony Blinken after it was revealed that Malley was put on unpaid leave last week after earlier this year being stripped of his security clearance amid an investigation into his handling of classified documents.

"The Department’s failure to inform Congress of this matter demonstrates at best a lack of candor, and at worst represents deliberate and potentially unlawful misinformation," the chairman wrote. "Given the gravity of the situation, it is imperative that the Department expeditiously provide a full and transparent accounting of the circumstances surrounding Special Envoy Malley’s clearance suspension and investigation and the Department’s statements to Congress regarding Special Envoy Malley."

The letter also requests that the White House make available to testify at a public hearing and provide a classified briefing on Capitol Hill by the end of July Acting Special Envoy for Iran Abram Paley and National Security Council Coordinator for the Middle East and North Africa Brett McGurk.