The two men and a woman were detained on Monday after officials became suspicious when they tried to take eight suitcases through airport security, heading for Malaysia via Portugal.

“Inside the cases were bags with water and baby eels,” the NVWA Dutch food and goods watchdog said.

“NVWA inspectors discovered 105kg of glass eels. That’s around 300,000 eels,’ the body said in a statement.

“The eels are to be released back into Dutch waters.”

Over the last four decades, critically endangered European eel populations have been devastated, falling by as much as 99% in some areas, according to EU figures.

Young transparent eels, known as “glass eels”, are particularly prized in Asia, where they may be fattened in farms, exceeding the price of caviar in the mid-2000s.