An international smuggling ring may have secretly shared blueprints for an advanced nuclear weapon with Iran, North Korea and other rogue countries, The Washington Post reported Sunday.

The now-defunct ring led by Pakistani scientist Abdul Qadeer Khan is previously known to have sold bomb-related parts to Libya, Iran and North Korea. A draft report by former top U.N. arms inspector David Albright says the smugglers also acquired designs for building a more sophisticated compact nuclear device that could be fitted on a type of ballistic missile used by Iran and other developing countries, according to the Post.

The drawings were discovered in 2006 on computers owned by Swiss businessmen; they were recently destroyed by the Swiss government under the supervision of the U.N. nuclear watchdog agency to keep them out of terrorists’ hands. But U.N. officials said they couldn’t rule out that the material had already been shared.

“These advanced nuclear weapons designs may have long ago been sold off to some of the most treacherous regimes in the world,” Albright wrote in the draft report, which was expected to be published later this week, the Post reported.

A spokesman for the Pakistani Embassy in Washington, Nadeem Kiani, did not rebut the report’s findings. “The government of Pakistan has adequately investigated allegations of nuclear proliferation by A.Q. Khan and shared the information with” the U.N.’s International Atomic Energy Agency, Kiani told the Post. “It considers the A.Q. Khan affair to be over.”