The tests are in effect a collective urine test and were commissioned by the local Sydsvenskan daily on water passing through water treatment centres which service the two cities in southern Sweden.
The tests are carried out by measuring the levels of various substances in the water and thereby producing an estimate for how many people use drugs.
The results show that 10,700 people in Malmö used cannabis on the Saturday night in question, some 1,340 people used amphetamines and 320 had used cocaine. The estimates are based on an assessment of average doses of the drugs.
The equivalent number for Lund was 1,370 for cannabis, 110 for amphetamines and 26 for cocaine.
According to the newspaper this is the first time this type of test has been carried out in Sweden.
Cannabis use is increasing sharply across Sweden, according to figures published in 2011, becoming by far the most common illegal drug.
According to one survey, 40 percent of boys at some inner-city Stockholm secondary schools have tried the drug and police estimates from 2007 indicate that some 25-30 tonnes are imported each year.
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