Switzerland's highest court is investigating claims that the Swiss ambassador to Luxembourg may have handled drugs money.
Peter Friederich has been in custody for three weeks following a tip-off from banks that he was involved in money-laundering activities.
The Federal Tribunal in the Swiss capital, Bern, said it was refusing to release 60-year-old Mr Friederich from custody, because he may have handled money for drug traffickers.
The court said Mr Friederich had transferred funds from his Luxembourg bank account to many other foreign accounts, the beneficiaries of which were known to local police for drugs trafficking.
'Artwork receipts'
When he transferred the money, which was often deposited in small amounts, he also kept a 3% commission.
The Luxembourg authorities questioned the origin of the funds, but Mr Friederich produced receipts claiming he had sold artworks to acquaintances.
He has now admitted forging those receipts but has stopped co-operating with the investigation.
The ambassador has been suspended from his post and will remain in custody until 15 August.