Secretary for Development Bernadette Linn said on Wednesday that water quality at two housing estates in Fanling has improved for some households following the installation of filtering nets and cleansing of water tanks and pipes.

The measures to improve water quality came after residents at Queen's Hill Estate and subsidised housing Shan Lai Court have complained of black particles in tap water.

Linn said some residents are now saying they no longer see any particles while others say there are fewer.

She conceded it's hard to say when exactly the particles would be completely gone but expects continued improvement going forward.

She said results of lab tests on the particles should be out this week – to help officials find out where they are coming from.

Once the source is clear, the government will, she said, give an open and frank account on the issue.

"I think it's taken some time because the tracing work has to be done seriously and in a scientific manner," Linn said after attending a meeting at the legislature.

"We can't just rush to get it done.

"What we did promptly was to test the water quality, that it's safe to use. Because if it wasn't safe, officials had to suspend supply completely.

"So we did what was the most pressing, and the Water Supplies Department is now speeding up on source tracing."

Linn reiterated that water supplies and housing officials have taken samples from the buildings' tanks and internal pipes and didn't find anything abnormal.

She said it's understandable for residents to be concerned about what she called abnormal water impurity and that they can get freshwater from temporary tanks on the streets.