The Swiss economics ministry is investigating the import of 173 kilogrammes of gold bullion suspected to have originated from the former Yugoslav president, Slobodan Milosevic.
A ministry spokesman confirmed an investigation was underway to discover whether the import contravened sanctions imposed against Yugoslavia between June 1999 and October 2000.
The announcement came as the prosecutor's office in Belgrade launched an investigation into reports that Milosevic had transferred an identical amount of gold out of Yugoslavia between September 21 and November 21 last year.
Yugoslav prosecutors have asked the police to find out if the money from the sale of the gold was transferred into bank accounts in Greece and Cyprus.
Swiss authorities have confirmed the gold import would only have been illegal if proceeds from its sale had made their way back to a state-held enterprise in Yugoslavia.
There is no indication that this was the case, the spokesman said.
The finance ministry confirmed on February 22 that 173 kilogrammes of gold had arrived at Zurich airport, but it said the import had been traced back to a state-owned Yugoslav mine.
swissinfo with agencies