The risk of viruses spreading through underground drainage systems is very low as the public does not come into contact with it.

This was the response from Secretary for the Environment, Transport & Works Dr Sarah Liao to a question in the Legislative Council this afternoon.

She said the presence of domestic sewage and trade effluent in communal drains in Dundas Street, Mong Kok, was probably caused by illegal expedient connections to private buildings.

It may also have been caused by the direct discharge of wastewater into the drains at roadsides or alleys.

Dr Liao stressed that there is no misconnection of the underground communal drainage system in the area. She said the Environmental Protection and Buildings Departments will step up their inspection of private buildings to look for expedient connections.

If any irregularities are found, owners will be asked to rectify the situation promptly. Prosecutions for illegal discharge of wastewater into the communal drainage system will also be initiated.

Dr Liao said in the last decade the Government has invested some $20 billion in sewage collection and treatment facilities. These are now handling about 2.5 million cubic metres of sewage daily, accounting for 95% of Hong Kong's sewage treatment. As a result, there has been significant improvement to water quality in many areas.

Meanwhile, Dr Liao said in view of the environmental problems that may be caused by the overflow of sewage from private treatment facilities of village houses in the New Territories, the Environmental Protection Department conducted over 670 special inspections in 2002. Those who breached the law will be prosecuted.

Last year, six people were convicted and ordered to pay fines ranging from $2,000 to $15,000.