TUNIS, Tunisia — A man linked by officials to the attack on the U.S. consulate in Benghazi has been conditionally released by a Tunisian judge due to lack of evidence, his lawyer said Tuesday.

The release of Ali Harzi, a 26-year-old Tunisian, appears to represent a blow to the investigation of the Sept. 11 attack on the consulate in Libya that killed the U.S. ambassador and three other Americans. The investigation in Libya itself has been stalled due to the weak central government in the face of the powerful militias, some of whom may have been involved in the attack.

Harzi was one of very few people in custody in relation to the attack. U.S. officials said in December that Egypt had also arrested a member of the Islamic Jihad group for possible links to the attack, but in general they lamented a lack of cooperation from local governments in their investigation and said most suspects remained free.