HONG KONG, Feb. 5 (Xinhua) -- Hong Kong's Centre for Health Protection (CHP) said on early Wednesday that it was investigating three cases of the novel coronavirus infection which were classified as local infection cases.

The three cases have brought the total number of confirmed cases in Hong Kong to 18.

All of the three patients had no travel history during the incubation period. "According to our preliminary epidemiological investigations, the three additional confirmed cases will be classified as local infection cases," a spokesman for the CHP said.

"The CHP strongly urged the public to maintain at all times strict personal and environmental hygiene which is key to personal protection against infection and prevention of the spread of the disease in the community," the spokesman said.