Federal regulators say a U.S. Citizen in custody in Yemen as a suspected al-Qaida member worked at five nuclear plant complexes.The Nuclear Regulatory Commission says it's investigating what access Sharif Mobley might have had to sensitive areas.But the commission says laborers aren't usually given sensitive information.Officials say the 26-year-old Mobley he was rounded up in an al-Qaida sweep in Yemen and shot two guards in a Yemeni hospital during an escape attempt.His parents say he is innocent.