U.S. authorities say four State Department officials placed on administrative leave after last year's deadly attack on the U.S. mission in Benghazi, Libya, will be allowed to return to work.

Among them is Eric Boswell, who served as assistant secretary of state for diplomatic security. State Department spokeswoman Marie Harf said Tuesday the officials will be reassigned to new jobs. Harf said an internal review concluded "there was no breach of duty" by the four employees.

The attack on the U.S. diplomatic outpost in Benghazi on September 11 of last year killed four Americans, including Ambassador Christopher Stevens.

A review by an independent board described a security vacuum in Libya after rebel forces toppled the decades-long regime of strongman Moammar Gadhafi. It singled out the State Department's Bureau of Diplomatic Security and Bureau of Near East Affairs for lacking cooperation and being confused about protection at the diplomatic post.

Republican Congressman Darrell Issa of California criticized Tuesday's announcement. Issa has been leading a congressional probe of the government's response to the attack. He said he will expand his investigation to include the department's decision to not discipline the four officials.