In a statement, German prosecutors said Wisser and Lerch "are suspected of helping Libya in the development and construction of gas centrifuges in order to produce highly enriched uranium for atomic weapons."
Wisser was arrested last week and is accused of brokering a deal in 2001 to provide Libya with nuclear equipment. According to the German statement, Wisser had been living in South Africa and received more than $1 million to arrange for a South African firm to manufacture the parts. It is unclear whether that firm is the one where Meyer works.
Lerch was named earlier this year by Malaysian authorities as a middleman in the Khan network who tried to obtain equipment for Libya's nuclear program from a South African manufacturer. The name of the manufacturer has not been made public.
His Swiss home was raided last week by authorities searching for documents and accounting records that may show a connection to Khan, according to the German investigators. Neither Wisser not Lerch has been formally charged, and neither could be reached for comment.
Lerch, who once worked for the German vacuum technology firm Leybold Heraeus, has surfaced in a number of nuclear proliferation investigations in Europe. A senior European security official said that Lerch had been investigated in the 1980s for his ties to Khan but was never charged. "It's an old network," the security official said.
Lerch's Swiss attorney, Federico A. Pedrazzini, said they had not spoken in recent weeks, and he declined to address the most recent allegations. Lerch has denied wrongdoing in the past.
The Khan network was exposed last year when Libya announced it was giving up on efforts to make weapons of mass destruction. As part of a deal with Britain and the United States, it agreed to come clean about where it purchased equipment and gained expertise.
Since then, the IAEA and others have been trying to crack the network but have had little success.
Khan, who amassed a personal fortune selling weapon designs to Libya and nuclear components to Iran, was pardoned by Pakistani President Pervez Musharraf -- a key U.S. ally. The IAEA hasn't been given access to Khan, and Pakistan has refused to let the agency do key investigative work in the country, something that has significantly slowed its efforts.
In two recent reports on Iran and Libya, the agency complained that it was unable to confirm details or identify sources without access to Khan or the ability to conduct sampling in Pakistan.
Khan's network operated mostly out of the United Arab Emirates and relied on services and suppliers in numerous countries, including Malaysia, which housed a centrifuge factory. The IAEA believes Khan was working with people in more than a dozen countries and suspected South Africa from early on.
South Africa had nuclear weapons until 1991, when the government voluntarily dismantled six completed bombs. It still has a domestic nuclear energy program and, experts say, the kind of sophisticated manufacturing machinery, expertise and industrial infrastructure sought by those seeking to build nuclear weaponry. South Africa also has one of the world's strictest anti-proliferation laws, with severe sentences and financial penalties for violators.
Timberg reported from Johannesburg. Correspondent Craig Whitlock in Berlin contributed to this report.
