The drug trafficking trial of the owner of the biggest cannabis-vending coffee shop in the Netherlands has been delayed for further investigation, the court said Thursday.

The trial in the district court in Middelburg, which had started Tuesday, was delayed indefinitely to probe possible new evidence that may point to a flaw in the "integrity" of the original investigation, said a court statement.

Meddy Willemsen, 58, is being prosecuted with 16 others, including a manager of his Checkpoint coffee shop in Terneuzen near the Belgian border and local suppliers, for allegedly having kept more than the permitted amount of cannabis on site.

Though technically illegal, the Netherlands decriminalised the consumption and possession of under five grammes (0.18 ounces) of cannabis in 1976 under a so-called "tolerance policy".

Cannabis cultivation and mass retail remain illegal and are in the hands of criminal organisations in a black-market business worth some two billion euros (three billion dollars) per year.

There are around 700 licensed coffee shops in the Netherlands which are allowed to keep no more than 500 grammes of cannabis on their premises, though this limit is often flouted.

The trial is widely seen as a test case in a country that has been toughening its stance on soft drug use.