Libya gave U.N. inspectors drawings of a nuclear weapon, the International Atomic Energy Agency (search) said Friday, the most concrete sign yet that Libya was at some point serious about building such arms.

"We have put those drawings under our seal, and they are secure," Mark Gwozdecky (search), chief spokesman for the U.N. nuclear watchdog agency, said without elaborating.

Agency inspectors are in Libya (search), along with a separate team of U.S. and British experts to take inventory of its nuclear arms program, part of plans to scrap the weapons of mass destruction that the country admitted to possessing last month.

"It's the first time anyone has acknowledged" that Libya entertained intentions of building such a weapon, said a diplomat who's familiar with the agency's work with Libya.

The diplomat, who spoke on condition of anonymity, said the drawings were not of a complete weapons system including a missile or other means of delivery but more like a warhead. He described it as "a device that goes boom, which can be put on a missile or can be put into a bomb form."

He said that members of the joint U.S.-British team would be taking the drawings out of Libya within the next few days to evaluate them.