Cathay Pacific was facing criticism yesterday for not being forthcoming with details of a tainted water problem, as it declined to disclose which aircraft and passengers were affected. Water samples collected from the tanks of 14 Cathay aircraft between June 10 and 18 were found to be unsatisfactory. Coliform bacteria, a commonly used indicator of hygiene, was detected at a level from less than 10 to 90 units per 100 millilitres of water. An aviation expert said that as the source of contamination remained unknown, aircraft of other airlines could also be at risk. The Health Department said all 14 affected aircraft would be disinfected after returning to Hong Kong by today. Results from the latest water samples were still pending yesterday. The department said on Thursday the source of contamination had not been identified. "Other airlines might be at risk, too," said Dr Eric Wong Tsun-tat, an aviation expert at Polytechnic University. "As the source of contamination has not been found yet, maintenance and service providers need to identify the root causes." Each component of an aircraft carries an expiry date. Wong said if expired components were still in use, bacteria could grow. A source close to the investigation said the incident had been complicated by the fact that aircraft water tanks held water from different airports, therefore problems could be caused by water from other countries. The source also said bacteria could have grown if water remaining in the tanks had not been removed before refilling them with fresh water. A Cathay cabin crew member showed the Post a list of affected aircraft. From June 10 to 18, they visited almost 50 cities in Asia, America, Europe and Africa. Cathay said the incident involved aircraft of "different types". According to data from the CAPA Centre for Aviation, Cathay has five groups of aircraft - the Airbus A330 and A340, and Boeing 747, 777-300 and 777-200. A spokesman for Cathay said affected aircraft were both "long- and short-haul" going to "various destinations", but she refused to specify aircraft types. The number of passengers affected was also not disclosed. Cathay said at least 60 bottles holding 1.5 litres of water each were used on a flight, and water from tanks was boiled. Medical sector lawmaker Dr Leung Ka-lau accused Cathay of "inadequate transparency". "It is always better to report the truth to passengers," Leung said. "There must be something wrong with the [water supply] system that led to the incident."