Lahore, June 1 : Nuclear bomb blueprints and manuals on how to manufacture weapons-grade uranium for warheads are feared to be in circulation on the international black market, The Guardian has quoted investigators tracking the world's most infamous nuclear smuggling racket, as saying.

Alarm about the sale of nuclear know-how follows the disclosure that the Swiss government, allegedly acting under United States' pressure, secretly destroyed tens of thousands of documents from a massive nuclear smuggling investigation.

The information was seized from the home and computers of Urs Tinner, a 43-year-old Swiss engineer who has been in custody for almost four years as a key suspect in the nuclear smuggling ring allegedly run by Dr Abdul Qadeer Khan.

The report said that Swiss President Pascal Couchepin stunned his compatriots last week by announcing that the Tinner files, believed to number around 30,000 documents, had been shredded.

The extraordinary move, prompting demands for a parliamentary inquiry, was warranted to prevent the documents "getting into the hands of a terrorist organisation or an unauthorised state", according to Couchepin.

However, there are widespread fears this has already happened or still could.

"We know that copies were made. Both US intelligence and the IAEA had been pursuing this with great urgency and diligence. But what happened to the other copies that Tinner made? It is worrisome that there are other plans floating around somewhere out there," the paper quoted Mark Fitzpatrick, an expert on the illicit networks at the United Kingdom-based International Institute of Strategic Studies (IISS), as saying.

Testimony at the 2006 trial of another nuclear-smuggling suspect in Germany alleged that Tinner told investigators he had nuclear bomb designs at his office in Switzerland. The blueprints were in digital form and are believed to have been copied on to the network's computers in Dubai.

"It's amazing these people had so much information, incredibly sensitive stuff on nuclear weaponisation and gas centrifuges," said David Albright, a Washington-based former UN weapons inspector.

In his first interview since 2004 with the western media this week, Dr Khan told the Guardian that the Swiss case proved that anyone seeking a nuclear bomb could easily obtain the wherewithal in the West.

While the Swiss government maintains the treasure trove of nuclear intelligence was destroyed for reasons of national security, the Americans may have been involved because Tinner is believed to have also been working for the CIA.

However, there is a view that destroying the evidence will jeopardize a successful prosecution of Tinner, whose brother Marco and father Friedrich have allegedly long been associated with the smuggling network. (ANI)