A new analysis of waste water in the Netherlands biggest cities shows that more people are using crystal meth (methamphetamine), the Telegraaf said on Thursday.

Researchers from Dutch institute KWR Watercycle Research Institute found four times the amount of crystal meth in waste water in Amsterdam than it did in 2012, the paper said. In Utrecht and Eindhoven the amount of the drug found had doubled over the six-year period.

There was also a slight increase in the amount of cocaine found in waste water, and the picture nationwide is ‘reasonably stable,’ the KWR said. The use of party drug MDMA, or ecstasy, remains the highest in Europe.

Experts said last year the Netherlands’ dominance in the ecstasy rankings is most likely due to drugs manufacturers flushing residues into the drains. The south of the country is known as a centre for ecstasy manufacture.

This year, the researchers found signs that drugs manufacture is also taking place in Utrecht, the Telegraaf said.