OAK RIDGE, Tenn. (AP) — The Department of Energy says it plans a probe into a possible security breach at the Y-12 nuclear plant in Oak Ridge.

According to the Knoxville News Sentinel (http://bit.ly/1pwCPGo), a Sept. 3 letter from the DOE says the incident was discovered in June and concerns "the potential mishandling and unauthorized access to classified information."

Further details weren't immediately available. The plant spokesman declined to comment.

The newspaper cited a Sept. 3 letter to Jim Haynes, the president of Consolidated Nuclear Security, the contractor that took over management at Y-12 in July.

Security has been a hot topic at the plant since a breach in 2012 when three protesters broke in to a secure area.

The letter says DOE officials will visit the plant in October as part of the investigation.