The Department of Health is investigating the possible source of contamination after test results of water samples collected from Cathay Pacific Airways aircraft were unsatisfactory.
Cathay Pacific, the Airport Authority and Hong Kong Aircraft Engineering Company are assisting in the probe.
In the airline's routine water surveillance programme, samples collected from 14 out of 22 aircraft from June 10 to 18 were found unsatisfactory and coliform organisms were detected at a level ranging from less than 10 to 90 colony-forming units per 100 millilitres.
The airline has cleaned and disinfected the water tanks of nine of the 14 affected aircraft.The other five will be treated when they return to Hong Kong before June 27. It has also suspended the use of potable water for the 14 affected aircraft and arranged bottled water onboard.
The 14 aircraft flew different routes and potable water was collected in Hong Kong or other airports. Four HAECO water tankers had filled the affected aircraft.
HAECO has conducted cleansing and disinfection of all its 11 water tankers.
Results of water samples collected from the three water filling points in the airport on June 1, 8 and 15 were normal while the result of another sample collected on June 22 is pending.
The department will closely monitor the situation.
