Three Swiss engineers suspected of giving nuclear weapons technology to a rogue network in Pakistan should face smuggling charges, a magistrate has said.
Andreas Mueller said his recommendation is based on a lengthy probe into an alleged nuclear smuggling ring.
He has submitted his report to federal prosecutors, who will decide whether to bring charges on violating Swiss non-proliferation laws.
The six-year federal probe against Urs Tinner, his brother Marco and their father Friedrich was slowed down after the Swiss government repeatedly ordered evidence destroyed in the case allegedly under pressure from senior US officials.
The Tinners are suspected of links to the nuclear smuggling network of Abdul Qadeer Khan - the creator of Pakistan's atomic bomb.
Mr Mueller told a news conference: "There are many parts. It's like a puzzle and if you put the puzzle together you get the whole picture. There is not (just) one piece of evidence, there are many pieces of evidence."
Mueller said the Tinners did not deny working for the Khan network, but claimed they did not know his aim was to produce nuclear weapons. He also said the Tinners had worked for the CIA since June 2003.
In June 2009, the Swiss government ordered the destruction of about 100 pages of evidence linked to Mueller's investigation of the Tinner family, saying they contained information that could have endangered national security and needed to be kept out of "the wrong hands."
The Cabinet, or Federal Council, said those documents were "the most explosive" material in the case's file of more than 1,000 pages. Copies of some of the shredded files have reportedly resurfaced and could form part of the case against the Tinners.
The documents are copies of files destroyed in 2007 under a previous order that led to protests from lawmakers and legal experts, who said the government had undermined the prosecution in the smuggling case. The copies were found in prosecutors' archives in December 2008.