A triumph for Dutch police quickly turned out to be an embarrassing mistake after they destroyed what they thought was a field of cannabis plants.
Police on Wednesday announced they had discovered a plantation of some 47,000 cannabis plants with a street value of 4.4m euros ($6.3m; £3.8m).
They had destroyed much of the crop when they were told the plants belonged to a respected school of agriculture.
They were a type of hemp, being grown as a fibre for use in textiles.
The hemp plants looked like cannabis, but contained only trace amounts of THC, the psychoactive substance found in marijuana.
They were being grown in the field near Lelystad, Flevoland province under licence by researchers from Wageningen University who were studying the hemp variety as a potential sustainable source of textiles.
"The street value from a drug point of view is less than zero," the university's Simon Vink told AP news agency.
Under Dutch law, cannabis is a controlled substance, and its large-scale production is illegal.
However a policy of tolerance is applied to individual users.