Three months of testing revealed the presence of illicit drugs in the wastewater in Auckland and Christchurch. (File photo).

Methamphetamine traces are the highest of the illicit drugs found in Auckland and Christchurch wastewater, police tests show.

The Institute of Environmental Science and Research [ESR] was commissioned by police in December to test sites in both cities to allow authorities to map drug-use patterns and give a clearer picture of where and when drugs are most commonly used.

Three months of testing found significantly higher quantities of methamphetamine than other drugs, with similar quantities in both Christchurch and Auckland sites. The tests cannot be traced to individuals.

One site in each city for was tested for one week a month. Five drugs were tested: methamphetamine, cocaine, a-PVP, MDMA and heroin.

READ MORE:

* Police seize large amount of methamphetamine in Auckland

* Largest ever Auckland Airport seizure of methamphetamine

* Methamphetamine supply and use continue to grow

The tests found traces of cocaine and MDMA in both cities and no trace of heroin and a-PVP, a synthetic drug sometimes broadly described as bath salts.

The Christchurch site represents about 120,000 more people than the Auckland site.

Across the three week-long sample periods, an average of 662g of methamphetamine was found in the Christchurch supply, and 704g in Auckland.

Cocaine quantities were higher at the Auckland site and MDMA quantities were significantly higher at the Christchurch site.

The data will be used as a baseline for future results. Police said due to the short period of testing, no solid conclusions could yet be drawn.

"While this report does include three months' worth of data, it is difficult to make meaningful analysis of the results until further data is available," assistant police commissioner Bill Searle said.

"However, we can see from the results that there is no alpha-PVP or heroin being found in either testing site. The absence of these drugs in the areas being tested is good news for agencies."

The Ministry of Health said the data would give authorities access to quantitative data allowing for a more accurate picture of drug use.

"The programme will also show if an area sees changes in drug use patterns as well as the introduction of a drug in an area where it has previously tested negative," director of mental health Dr John Crawshaw said.

"This information will help [the] Government consider responses to the needs identified in the results."

Wastewater testing for drug use has become more commonplace in recent years as it provides more accurate data than self-reported drug use.

A Massey University study conducted in Auckland in 2014, released earlier this month, also found that methamphetamine was the most commonly used drug.

A nationwide wastewater testing programme is under way in Australia, with the first results expected soon.

Marijuana is not included because it requires extra testing.