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.

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.