An extremely sensitive issue is the unsolved explosion at Khobar Towers, the building in Saudi Arabia that was blown up in June 1996, killing 19 American servicemen.

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The U.S. airmen were killed when a truck bomb exploded shortly before 10 p.m. on June 25, 1996, outside the Khobar Towers, their military housing complex near Dhahran, Saudi Arabia.

CNN: Khobar Towers indictments returned

Other U.S. officials said the United States has long suspected members of Iranian security forces of being linked to the attack on Khobar Towers at the King Abdul Aziz air base.

CNN: Khobar Towers indictments returned