The government has given reassurances that the freshwater supply at two housing estates in Fanling is neither toxic nor carcinogenic.

Residents of Queen's Hill Estate and Shan Lai Court have complained of black specks in their water, with officials saying the substance is bitumen and resin that had been used in the past to coat pipes and valves.

The Water Supplies Department said on Friday that samples taken from water tanks in the two estates have come back clear.

Between Friday last week and this Thursday, it tested the freshwater supply at a total of 13 blocks at the estates and found no toxic contaminates or carcinogens.

Officials said they would review maintenance and flushing records with estate management companies and the Housing Department to help determine the origin of the black particles and then get rid of them.