Police will start an investigation this week of mainland officers' apparent enforcement actions on Hong Kong territory, which include allegedly dragging protesters and journalists into the mainland during a protest at the Lo Wu border last weekend. The Legislative Council security panel will hold a special meeting this Friday to discuss the apparent harsh treatment of activists and reporters. Mainland police detained four protesters and two journalists from Hong Kong for three hours after a protest at the Lo Wu immigration control point in support of jailed dissident Liu Xiaobo on Sunday. Hong Kong police failed to stop mainland public security officers from apparently dragging protesters across into the Shenzhen side of the border bridge. A police spokeswoman said yesterday the New Territories North regional crime unit was investigating the case, which comes after Hong Kong police were condemned by lawmakers and protesters for ignoring a serious matter that might have undermined their jurisdiction. Hong Kong police officers initially said they had not seen any mainland public security officers exercise jurisdiction on the Hong Kong side of the border on Sunday night - but later revised that statement to say they did not see any uniformed mainland law enforcement officers exercise jurisdiction on the Hong Kong side. A spokeswoman for the 21 activists who took part in the protest, Yu Yat-sum, said yesterday she received a call from police to give them a statement on the incident. 'We are willing to co-operate in the investigation by the police and Legco,' Yu said. She was hoping to speak to all the protesters so they could make statements to police and put their side to the inquiry. Meanwhile, Ming Pao Daily News, the Chinese newspaper that had two of its journalists detained in the incident, said yesterday it had received a call from police on the matter. The Apple Daily - which published photographs of alleged plainclothes mainland officers taking enforcement action on the Hong Kong side - was also contacted by police. The Legislative Council security panel will ask the city's police to hand over videos and photos taken at the scene to determine whether mainland plainclothes officers crossed the border, grabbed the activists' banner and dragged them to the Shenzhen side.