MDMA, often sold as ecstasy, is the stimulant drug of choice for young people and is resurging throughout Europe following a sharp decline, says the EU's drug agency.

The findings are part of a larger 84-page trend report out Tuesday (31 May) by the Lisbon-based European Monitoring Centre for Drugs and Drug Addiction (EMCDDA).

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"MDMA is moving into more mainstream social settings and is increasingly available via online markets," EMCDDA director Alexis Goosdeel said in a statement.

Around 2.5 million people last year used the synthetic substance. Of those, 2.1 million were adults aged 15 to 34.

Most ecstasy tablets sold in the EU have in the past been found to contain low to no trace of MDMA. But this is now changing.

Reports indicate much of it is produced around the Netherlands and sold in high-dose tablets, powder or in crystal form.

An estimated 6.1 million tablets were seized in police raids in 2014, more than twice that in 2009.

And in another indication of its increasing prevalence, residues of MDMA in municipal waste-water were found to be higher in 2015 than in 2011, according to a 2015 multi-city study.

The study suggests the surge in the drug is part of a marketing strategy after a decline in sales.

Health problems associated with the drug are not common although risks increase when MDMA is combined with other drugs.

"Overall the current level of serious acute harms associated with the use of MDMA appears to be low," notes a separate EMCDDA report dedicated to the drug.

EU states do report occasional MDMA-related deaths. Ireland, for instance, reported 14 MDMA related deaths and France five. However, experts say these incidents are usually down to individuals taking tablets that contain other harmful substances alongside MDMA.

Opioids provoke most overdose deaths

Separately, the report documented that 16.6 million people in the same 15-34 age group smoked cannabis, and another 2.4 million snorted cocaine.

Amphetamines, opioids and new substances were the least used.

But opioids such as heroin were implicated in 82 percent of the 6,800 fatal overdoses recorded in the EU in 2014. The vast majority were men, mostly in northern Europe and the UK.

Conservative estimates value the retail market for illicit drugs in the European Union in 2013 at €24.3 billion. Around 38 percent is from cannabis, followed by heroin (28 percent) and cocaine (24 percent).