The headquarters of the Albert Heijn supermarket chain in Zaandam has been plagued by threatening letters containing white powder in recent weeks, the Telegraaf reports on Thursday.

Two letters arrived in Thursday morning’s post delivery, bringing the total to six over the past two months, police said.
A spokesman for the country’s food retail market leader said the letters were extremely irritating. ‘The post room workers get upset, even though up to now the letters have been a false alarm,’ he said. ‘It is a complete mystery why the letters are being sent to us.’