Police have dropped some of the disorderly conduct charges against three university students who stormed a public consultation forum on the government's plan to scrap by-elections. Leo Tang Kin-wah, 22, a member of the Hong Kong Federation of Students, said he had received a letter from police yesterday via his lawyer. The letter said the charges of acting in a disorderly manner at a public gathering against him, Daisy Chan Sin-ying, 22, a fellow federation member, and Napo Wong Weng-chi, 24, a member of the League of Social Democrats, had been dropped 'due to insufficient evidence'. However, Tang and Chan still face a less serious charge of disorderly conduct in a public place, which has been dropped against Wong. The two sets of disorderly conduct charges remain levelled against three other activists, including radical legislator 'Long Hair' Leung Kwok-hung. The six were among seven people arrested after protesters gatecrashed a public forum on the by-election plans. The forum was held at the Science Museum in Tsim Sha Tsui on September 1. That sparked scuffles with security guards and forum participants. The forum speaker, then-constitutional affairs chief Stephen Lam Sui-lung, and others were forced to flee backstage. The six accused appeared at Kowloon City Court on the day of arrest, where they all denied the charges. They were later released on bail. The seventh accused, Penny Keung Ling-cheung, Leung's aide, was arrested for allegedly hurling dog biscuits at Lam as he entered the museum. She was released on bail of HK$150 before the court hearing. The three cleared activists were due to appear in court on November 24 with their co-accused, Leung, League member Yung Wai-tong, 60, and screenwriter and internet radio host Wong Yeung-tat, 32. Last month, two League of Social Democrats activists were acquitted of disorderly conduct for throwing a bottle and a bag of corn flour into Beijing's liaison office last year. The court ruled that they had breached the social order but not the peace. A month earlier, two other League of Social Democrats activists were charged over an incident in March in which Chief Executive Donald Tsang Yam-kuen said he was struck on the chest. They were later acquitted because of insufficient evidence.