US officials are probing the case of a suspected terrorist held in Yemen after evidence revealed he had worked at several nuclear plants in the US, Xinhua reported.

Sharif Mobley, a US citizen, was nabbed in an anti-terror operation in Yemen this month, Yemeni authorities said. He is suspected of having ties with the Al Qaeda terrorist network.

US Nuclear Regulatory Commission Friday confirmed to media that Mobley had worked for contractors hired by five nuclear plants in Maryland, New Jersey and Pennsylvania between 2002 and 2008. He was mostly involved in maintenance work.

Media reports cited unnamed US officials as saying that investigators are looking at whether Mobley had access to sensitive material or information.

Mobley, 26, is of Somali origin, and was born in Buena in New Jersey. After his arrest, he complained of being ill, and was taken to a hospital in Sanaa over the weekend. He shot dead a guard after grabbing a gun from the security officials at the hospital. He was later recaptured.