Colombia's public prosecutor is to hold an inquiry into allegations that a Swiss mediator transported ransom money to rebels during hostage negotiations.
Mario Iguaran announced there would be a probe into whether Jean-Pierre Gontard carried $500,000 (SFr503,000) for the Revolutionary Armed Forces of Colombia (Farc) while negotiating the release of two employees of Swiss pharmaceuticals giant Novartis.
The investigations centre on documents reportedly found on the computer of the former Farc number two, who was killed by the Colombian army on March 1 in Ecuador.
Farc is considered a terrorist group by the United States and the European Union.
The Swiss foreign ministry says Gontard took part in a "facilitation" mission in 2000 in which he accompanied the Mexican ambassador to meet the head of the Farc and request the release of the two people ahead of an eventual ransom payment.
The release took place in 2001, in the presence of a senior member of the Colombian police force.
"A payment took place several months later, after discussions, which are reported on Mr Reyes's computer," the foreign ministry has said in a statement.
The inquiry follows the release by the Colombian army of 15 Farc-held hostages at the start of July, after which the Colombian authorities halted further mediation by Switzerland, France and Spain for the release of hostages.
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