Police chief Andy Tsang Wai-hung has defended the force's decision not to investigate the alleged domestic violence on Chief Executive Leung Chun-ying's eldest daughter, saying it could not possibly look into every allegation on the internet. Tsang was responding to questions about why the police did not pursue the case after Leung Chai-yan, 23, wrote on her Facebook page on Tuesday that her mother Regina Leung Tong Ching-yi had assaulted her. Police officers and an ambulance arrived outside the Government House on Tuesday morning after they received a 999 emergency call. The officers left the scene shortly after without launching an investigation, triggering criticism from some members of the community. The chief executive has openly denied the allegation against his wife and said their daughter had been suffering from emotional instability since she went to Britain to study. Chai-yan has since returned to Hong Kong. "There are many things posted onto the internet. It is impossible to launch an investigation whenever someone says something online. You wouldn't want to be investigated for anything you wrote on the internet, would you?" Tsang replied when asked by a reporter why police did not look into Chai-yan's allegation. "I do not want to speculate on whether violence has taken place, or what sort of violence if any," he said. Tsang was speaking after the government's fight crime conference. His comments came as new social media postings, apparently from Chai-yan, appeared on the internet yesterday saying she was "running away". The authenticity of the postings could not be verified.