A Geneva judge has wrapped up a probe into money laundering allegations against Raul Salinas, the brother of former Mexican president Carlos Salinas.
Judge Paul Perraudin, in charge of the investigation since 1999, has now asked Swiss prosecutors to pass the case on to his Mexican counterparts.
Perraudin refused to reveal details of his investigation, which was probing allegations that Raul Salinas laundered $130 million (SFr208 million) through Swiss banks.
The Swiss authorities froze the money in 1998 on suspicion that it came from drug cartels in Mexico and Colombia.
The money will remain frozen in six banks in Geneva and Zurich until Mexico can confirm whether it came from criminal activities. If the funds are found to have stemmed from corruption, they would be returned to Mexico.
Pierre-André Béguin, Raul Salinas' lawyer, said he would be appealing against Perraudin's decision, arguing that the investigation is incomplete and that further witnesses should be questioned.
Raul Salinas has denied taking pay-offs to help drug traffickers and has accused Swiss prosecutors of exaggerating the size of his bank accounts. He claims the money came from Mexican business leaders for investment projects.
Convicted of murder
He is serving a 27-year sentence for ordering the 1994 murder of his ex-brother-in-law, Jose Francisco Ruiz Massieu, who was secretary-general of Mexico's former ruling party, the Industrial Revolutionary Party.
The Salinas affair first exploded in Switzerland in 1995 when authorities launched an investigation following a tip-off from the US Drug Enforcement Administration.
Raul Salinas' wife, Paulina Castanon, and her brother Antonio Castanon, were arrested in November 1995 after they tried to make a withdrawal from a Geneva bank using fake identification papers.
Swiss prosecutors later dropped the case against them because their alleged involvement in drug offences in Mexico and money laundering charges in Switzerland could not be proved. They were paid compensation for their month-long detention.
Perraudin formally charged Raul Salinas with money laundering after visiting him in Mexico's Almoloya de Juarez maximum-security jail in July last year.
However, the Swiss investigation has been bedevilled with difficulties. A key witness "disappeared" in November last year shortly before he was due to fly to Geneva.
swissinfo with agencies