"[Mobley] satisfied federal security background checks required to work in the US nuclear industry as recently as 2008," said PSEG Nuclear spokesman Joe Delmar in a statement.
Delmar confirmed Mobley's work for contractors at the company's three South Jersey reactors, Salem 1 and 2, as well as Hope Creek. In addition, records show he worked for contractors at two other nuclear plants in the region, in Maryland and Pennsylvania.
But a federal law enforcement source told NBC News they do not believe he learned anything as a result of his work as a laborer that would be useful to terrorists.
Mobley moved to Yemen a couple of years ago, according to a report by NBCPhiladephia. He was apparently captured during a police raid, and is alleged to have shot a police guard at a hospital where he had been taken, in an unsuccessful escape attempt.
While reports from the Mideast describe his as an American home-grown terrorist, the federal law enforcement source also told NBC News that it's "doubtful" Mobley had any actual connection with al Qaeda.
"It appears he was never brought into the mix" of al Qaeda, according to this official, who described him as someone who aspired to join the terror network.
Meanwhile, New Jersey's Muslim community is dismayed by word of Mobley's radical turn.
"We're just regular people, just trying to live a regular life here," Ahmad Atiyeh, 19, of Syracuse, NY said of his fellow Muslim-Americans.
And Dr. Hani Awadallah, of the Arab American Civic Organization in Paterson, NJ, said any religion can have it radicals--noting the hundreds who died in a suicide pact with the Rev. Jim Jones in Guyana.
"You don't really have to be a Muslim, you really can be anything and become radicalized," said Dr. Awadallah.
Atiyeh, when asked what he might say to a friend who was turning radical, responded "Just go to the mosque and pray."