Officers said the U.S. government plans to designate Abu Sufian bin Qumu and his group -- Ansar al-Sharia in the Libyan city of Darnah -- as foreign terrorists because militants under Qumu's command participated in the attack that killed U.S. Ambassador J. Christopher Stevens and three others, the Washington Post reported.
The designations were disclosed to Congress last week, the New York Times said Thursday. The action is expected to be released publicly by the State Department on Friday.
Witnesses have told officials that Qumu's men were in Benghazi before the Sept. 11, 2012, consulate attack, the officials told the Post. Whether their presence was by design or coincidence wasn't clear.
The State Department is expected to link Ansar al-Sharia to the Benghazi attack when it designates branches of the organization in Darnah, Benghazi and Tunisia as foreign terrorist organizations soon, the Post reported Tuesday.
The Post said Qumu and militia leaders Ahmed Abu Khattala and Seif Allah bin Hassine will be identified as "specially designated global terrorists," a determination that allows U.S. officials to freeze the trio's financial assets and to bar U.S. citizens and companies from conducting business with them.
Qumu was released from the U.S. prison at Guantanamo Bay in 2007 and sent to Libya, where he was held until the Libyan government released him in 2008.
About a dozen criminal complaints have been filed in the Benghazi case and more are expected. Khattala is named in a complaint.
The FBI did not comment, the Post said.
The Post said U.S. officials also were investigating whether any of the people involved in the consulate raid played a part in the death of Ronnie Smith, a U.S. schoolteacher killed while jogging in Benghazi last month.