Lake snow may have infected a fourth lake - Lake Hawea.
The slime has already been confirmed in Lakes Wanaka, Wakatipu and Coleridge.
Yesterday, Guardians of Lake Hawea member Don Robertson told the Otago Daily Times an analysis had not been done but a fisherman had reported a similar slime in Lake Hawea.
Lake snow (also known as lake snot), thought to be caused by the algae Cyclotella bodanica, has been present in Lake Wanaka since 2004 and had recently been found in Lake Wakatipu.
A report from the Otago Regional Council found a number of possible reasons for the increase of the algae which produced the snow.
Likely causes included the presence of an introduced water flea, warming of the lake caused by climate change and an increase in nutrients entering the lakes.
Management of the issue could not start until a definite cause for the increase in the algae was discovered, the report said.
Non-toxic to humans, lake snow fouled fishing lines and clogged water filters and appliances using lake water.
It was possible the algae was non-native and was introduced to the lakes quite recently, the report found.
Otago Regional Council director of engineering, hazards and science Gavin Palmer said he was unaware of reports a similar slime had been found in Lake Hawea. Despite it being an aesthetic rather than public heath issue, the council was still concerned, he said.
DNA from the algae found in the lakes would be tested against samples collected overseas, which allowed scientists to determine how long the algae had been in New Zealand, Mr Palmer said.
Trophic studies on Lakes Wanaka, Hawea and Wakatipu would start this month and information collected would help the council and scientists determine what was happening in the lakes, he said.
''We don't know enough at the moment and the purpose of the report is to put out everything we know about lake snow.''
Otago Fish and Game chief executive Niall Watson was concerned about the presence of lake snow in Lake Wakatipu after the effect it had had on anglers in Lake Wanaka.
Data collected by Fish and Game found fishing attracted more than 20,000 people to the lakes each year, Mr Watson said. If the problem got worse, many would choose to fish elsewhere, he said.
A letter would be sent to Environment Minister Nick Smith asking for urgent action on the issue, Mr Watson said.
