Four passengers on board a Thai Airways plane at Hong Kong airport were injured last night when the aircraft apparently rolled backwards out of its parking bay for 30 metres. Flight TG608 from Phuket to Hong Kong had reportedly just parked up at 7.20pm and the ground crew was about to secure it in place with wheel chocks when the incident happened. Police said airport staff told officers that the four injured passengers had fallen over when the plane began moving again. A 37-year-old mainland woman was taken to North Lantau Hospital with neck injuries. She was later transferred to Princess Margaret Hospital, Kwai Chung. An Airport Authority spokesman said a man and two women, aged 46 to 59, were also examined by medical staff but did not require hospital treatment for their injuries. A figure for the number of passengers on the plane was unavailable last night. An aircraft mechanic at Chek Lap Kok suggested the incident may have been the result of a misunderstanding between the pilots and the ground crew and was something he had only come across once or twice in his 30 years of service. He said that usually after a plane was parked up the pilots would turn off the engines and apply the parking brake, before the ground crew applied the wheel chocks. Once the chocks were in position, the pilots would be notified and the parking brake released. He believed the brake may have been released prematurely, and then the plane rolled back down a slight incline. "I remember it happened once in about 1999 at the airport, with the plane sliding back about 30 metres that time too." He advised passengers to keep their seat belts fastened until the signal to unbuckle came on. A Civil Aviation Department spokeswoman said it would look into what had happened before deciding what action to take.