Drug traffickers are increasingly using threats and bribery to press lorry drivers into transporting their illegal cargo, an investigation by RTL Nieuws has found.

The broadcaster said it had spoken to more than 50 drivers who had been contacted by drugs gangs in the past three years.

The approaches varied widely. One driver found a note on his windscreen promising large sums of money to carry a shipment, while another was held up by armed men while couriers unloaded a stash of drugs that had been hidden in the trailer.

Justice minister Dilan Yesilgöz said she was “very concerned” by the reports. The government has earmarked an extra €500,000 for training to help haulage firms recognise the signs of infiltration by drug gangs and learn how to act on them.

“They also need to know where they can ask for help if things go wrong,” Yesilgöz said. “I’ve seen that this training works.”

Police set up a four-man unit known as the Transport Facilitated Organised Crime (TFOC) two years ago to prevent and investigate drug crime in the haulage sector.

Michael Dop, a member of the team, told RTL it receives around 150 reports a year from businesses, almost all of which expose criminal activity.

“As drug crime grows, the number of incidents against lorry drivers is increasing,” Dop said.

On Tuesday customs officers in Zeeland found more than 900kg of cocaine stored at a business in Middelburg and the harbour in Vlissingen. The drugs, with a street value of €70 million, were destroyed.

In the last two weeks two batches of cocaine totalling 1,308kg were discovered in shipments of bananas during routine inspections in Vlissingen, Omroep Zeeland reported.