The surgeon who took a mobile-phone call while performing keyhole surgery to remove a polyp from a taxi driver's colon was talking to another doctor, an investigation has shown. The patient's colon wall was pierced during the operation and he had to undergo a second operation for inflammation of the abdominal wall. However, the Queen Mary Hospital surgeon, surnamed Tung, who has admitted to the Hospital Authority's Professional Standards Committee for the first time having taken the call, stressed that the conversation was brief, the South China Morning Post has learned. Dr Tung also denied that the May 13 phone call - from a Health Department medical officer - concerned the purchase of a car. However, the patient, Chung Chi-cheong, has claimed the conversation was about a car. He told the team investigating his complaint that he had heard the doctor say a Japanese car he had seen, valued at $160,000, was not good and he preferred a silver BMW. Vehicle records showed the surgeon bought a silver BMW on May 5, a week before the operation. A source told the Post: 'If he hadn't talked about the car, how come the patient was able to recall such details?' Both the Hospital Authority and its Public Complaints Committee are investigating the case, which came to light when Mr Chung complained on television after Queen Mary Hospital failed to settle his case. In a letter to the committee accompanied by his phone records, the Health Department medical officer said he called at 11.45am. The officer testified Dr Tung said he was performing surgery. There was a 'very brief' conversation and Dr Tung asked him to hold. Minutes later, the surgeon told him he was still busy operating and asked him to call back later. Dr Tung also told the committee that he did not make a phone call during the operation. Phone records show that the surgeon made an outgoing call at 10.45am for six minutes. He said the call was made before the operation and that it was practically impossible to call during surgery. The source said: 'The doctor has breached hospital rules. A guideline issued in 1994 stated very clearly that all mobile phones are banned in the operating theatre. 'However, we cannot come to the conclusion that the phone call caused the complication in the surgery. Breaking the colon wall is a known complication in this kind of surgery.' Meanwhile, more than 100 doctors, patients and medical professionals have sent letters to the Hospital Authority in support of the accused doctor.