The Dunedin City Council has been testing mud-tank waste after test results in April showed low-risk levels of asbestos at the Green Island Landfill.
Since then, contractors have been wearing protective equipment when cleaning the city's mud-tanks, as a precaution.
Council transport group manager Richard Saunders said further random sampling of waste in seven mud-tanks found low levels of asbestos in at least two more tanks.
The council was working with an independent laboratory and consultant to review the results and advise on precautions when working with mud-tank waste, Mr Saunders said.
As the asbestos was confined to mud-tank waste there was no risk to the public, he said.
Safety controls were in place for workers when they cleaned the tanks.
''The initial report has been presented to our maintenance contractor and we are working with them to develop safe work practices using the report's recommendations and in accordance with WorkSafe guidelines.''
