A German engineer has been arrested in Switzerland on suspicion of being involved in Libya's previous efforts to develop nuclear weapons.
Gotthard L is suspected of helping to develop a gas centrifuge
The 61-year-old, named as Gotthard L, was detained under an international arrest warrant last Saturday.
He is believed to have received up to $4m for his work on developing a uranium-enriching device.
He is suspected of being part of a nuclear components network ran by Pakistani scientist Abdul Qadeer Khan.
Dr Khan, the father of Pakistan's nuclear weapons programme, admitted last February passing nuclear technology to other countries.
The German engineer was arrested by Swiss police in the canton of St Gallen.
His full identity was not released but reports have named him as Gotthard Lerch.
German prosecutors accuse him of helping to develop a gas centrifuge to enrich uranium for use in nuclear weapons between 2001 and 2003.
His arrest follows others linked to what investigators believe is a network of mainly Dubai-based engineers who supplied nuclear equipment and know-how to Libya.
Gerhard Wisser, a German national, and Urs Tinner, a Swiss engineer, have recently been arrested on suspicion of involvement in the ring.
Mr Tahir is accused of being a middleman between the network and Libya
The three are alleged to have been associated with Buhary Seyed Abu Tahir, a Sri Lankan, who prosecutors said was a middleman between the network and Libya.
Libyan leader Muammar Gaddafi renounced his banned weapons programs in December 2003 in a dramatic turnaround meant to help rebuild relations with the West.