The police chief yesterday vowed to raise a strong protest if any mainland law enforcement officers were found exercising their duties in Hong Kong. Commissioner Dick Lee Ming-kwai made the remarks amid concerns that two public security officers were caught on duty with five other mainlanders at Mount Davis, Pokfulam, on Wednesday night. Mr Lee said the Hong Kong force and the Public Security Ministry had agreed in 1997 to follow the Interpol protocol to pursue cross-border crimes and not to enforce duties in each other's jurisdictions. 'If it is true that someone has failed to follow the agreement, we would raise a strong protest,' Mr Lee said. While Beijing's Public Security Ministry was yesterday quoted in the Wen Wei Po newspaper as denying having sent any officers to Hong Kong to pursue crime cases, Mr Lee said he was still waiting for clarification from the mainland authorities. The incident came to light after the police received a report of people acting suspiciously on Mount Davis Road on Wednesday night. Police found seven mainlanders at the scene, including two who claimed they were Guangdong Public Security officers monitoring a suspect. The seven men were taken to Western police station. They were released but asked to report back when the force received information from the Guangdong authorities. Meanwhile, Guangdong Public Security has still failed to clarify allegations over a separate incursion case in which a mainland law officer was believed to have exercised his duty over a fraud case in Hong Kong in 2001. The lack of co-operation forced police to complete their inquiry without the benefit of a response. The Department of Justice concluded last year that there was insufficient evidence to suggest any criminal element in the case. In the incident, law officer He Liang allegedly exchanged material relating to a fraud case at a hotel in Wan Chai with the daughter of Hong Kong man Chan Tsz-cheung, who was detained in Guangdong over the deception case involving an indirect loan from state-backed Guangnan (Holdings). But Mr He had not revealed his identity during the meeting. Chan's daughter, Joyce Chan Yuet-chun, said she was later told that Mr He was a public security officer. Chan was later charged and stood trial in Shenzhen in April. He pleaded not guilty and is still awaiting a verdict.