Spanish scientists said Wednesday they have detected cocaine, ecstasy and six other drugs in the waters of a nature reserve, and warned of a possible risk to wildlife and public health.

Investigators from the University of Valencia analysed the water in canals and irrigation channels of eastern Spain's Albufera Natural Park, a major wetlands region, for the presence of 14 kinds of drugs, Spain's Scientific Information and News Service (SINC) said.

The scientists looked for the residue these drugs leave behind in human urine after they have been taken, and which end up in the water.

The results showed the presence of eight kinds of drugs, particularly cocaine and ecstasy, SINC said.

"The results confirm the presence of drugs such as cocaine, amphetamines, codeine, morphine and cannabis in the surface waters ... at levels ranging between 0.06 and 78.78 nanogrammes per litre," said Yolanda Pico, lead author of the study.

A nanogramme is one billionth of a gramme.

"Cocaine and its metabolites were ubiquitous in all the samples taken, while ecstasy was also found very frequently," said Pico, a senior professor at Valencia University's Department of Nutrition and Bromatology.

The study, also published in the journal Analytical and Bioanalytical Chemistry, showed that the highest concentration was found in the north of the park in an area where waste water is regularly discharged and which has the highest population density as well as industry and nightclubs.

The scientists warned of the dangers that these substances could have on people and on the environment, although no exhaustive tests have been carried out.

"The health problems potentially caused by consuming these, added to the fact that these residues are still strongly pharmacologically active, may have consequences for land organisms and aquatic fauna," Pico said.

The Albufera Natural Park is one of the most important wetlands in Europe because of its biodiversity of flora and fauna, and because it is a key area for migratory birds.

But "paradoxically, the park is surrounded by cities, industries, farms, shopping malls and leisure centres," the study said.