June 20 (Bloomberg) -- Pakistan said its investigation into nuclear scientist Abdul Qadeer Khan's smuggling ring is closed and it has no knowledge of blueprints for an atomic device found on computers linked to his network.

The government ``carried out a thorough debriefing'' of Khan after he confessed to selling nuclear weapons technology to Iran, Libya and North Korea in 2004, Nadeem Kiani, a press attaché at the Pakistani Embassy in Washington, wrote in USA Today. ``As far as Pakistan is concerned, the A.Q. Khan episode is closed. There will be no repeat of it.''

Khan, regarded as the father of Pakistan's nuclear program, has been under house arrest in the capital, Islamabad, for four years. Pakistan has refused requests from the U.S. and the United Nations nuclear watchdog to question Khan about the extent of his activities and how he evaded international controls.

Khan's network may also have sold blueprints for a compact nuclear device that could be mounted on a type of ballistic missile owned by countries such as Iran, the Washington Post reported last month, citing a draft report by former UN arms inspector David Albright.

Albright said Pakistan must let the U.S. and the International Atomic Energy Agency question Khan over the possible sale of the blueprints, which were discovered in 2006 on computers belonging to Swiss associates of the scientist, according to the report.

Nuclear Weapon

``Pakistan has no knowledge of the design of a compact nuclear weapon, reportedly found in some computers in Switzerland,'' Kiani said in the opinion piece yesterday, written in response to an editorial in the newspaper. ``Dr. Khan has also expressed ignorance of these.''

Pakistan has already shared information it gleaned from Khan with the U.S. and the IAEA, Kiani added. ``Direct access'' to the scientist isn't possible ``because he still knows important details of Pakistan's strategic deterrent.''

President Pervez Musharraf placed Khan under house arrest in 2004 after the IAEA presented his administration with evidence of the nuclear technology sales.

On national television, Khan took full responsibility for the sales, saying Pakistan's army, then headed by Musharraf, had no knowledge of them. Musharraf pardoned Khan the following day, avoiding a trial and sparing him imprisonment.

The country's coalition government, which defeated Musharraf loyalists in February's national elections, is under public pressure to free Khan, who is a national hero for his role in Pakistan's development of an atomic bomb.

In recent weeks, he has been allowed to give media interviews and has recanted his earlier confession.

Khan ``remains under constant guard,'' Kiani wrote. ``There is no letting up of vigilance.''

To contact the reporter on this story: Ed Johnson in Sydney at ejohnson28@bloomberg.net.

Last Updated: June 19, 2008 21:38 EDT