A drug gang which manufactured about 200 kilograms of heroin had been betrayed by two of its members, a High Court jury was told yesterday. Prosecutor Peter Chapman said the two prime prosecution witnesses had been involved in the operation and would testify under immunity. Two factories were used by the gang, one near Sha Tin and the other in Yuen Long, it was alleged. Mr Chapman said about 100 kilograms of heroin was manufactured in each factory between March and December 1986. The gang of seven men had included a chemist who was responsible for the manufacturing process. The heroin would then be packed and distributed, Mr Chapman said. Lau Kwok-ching, 40, Liu Kwok-keung, 37, Lau Kwok-hung, 36, and Mak Kam-chuen, 37, all deny a single charge of conspiring to manufacture heroin. The trial, before Deputy Judge Clare-Marie Beeson, continues today.