THE Commissioner of Police has pledged a thorough inquiry into the alleged police beating of two off-duty customs officers, one of whom is now in hospital. Mr Li Kwan-ha said yesterday he had instructed the Complaints Against the Police Office (CAPO) to mount the investigation. He appealed for witnesses. ''The investigation will be completed as quickly as possible and the findings reported to the Police Complaints Committee,'' Mr Li said. CAPO has given priority to the case. The victims claimed they were punched, kicked, and beaten with batons shortly after they tried to stop police using excessive force in an unrelated arrest outside a Hunghom restaurant. The victims were later released on bail of $5,000 each without charge. Customs officer Mr Yeung Hak-kwong, 28, was admitted to Prince of Wales Hospital on Thursday night with lung injuries. CAPO's Senior Staff Officer Mr Ross Williams said he had deployed extra manpower to deal with the complaint. ''We are keen about investigating this complaint but I would not speculate on how long that would take,'' he said. Superintendent Sean Healy of the Kowloon West Emergency Unit said his officers had already assisted inquiries by Kowloon City District Crime Squad over alleged criminal misconduct by the customs officers. Hunghom Divisional Commander Superintendent Michael Pang Yan-wing said he was not aware if any of his staff had been summoned by CAPO. The incident is seen to worsen relations between the two forces. Customs officers are understood to be jealous of police dominance and credit in the joint Anti-Smuggling Task Force, while police detectives have privately complained of being kept in the dark about customs drug raids. But senior officials from the two forces yesterday dismissed suggestions that there had been conflicts in anti-smuggling and narcotics operations. Senior Superintendent Tsang Hing-kam of the Customs Marine and Land Enforcement Command stressed the task force was united with a good working atmosphere. ''Members find themselves working in a cohesive environment like a big family,'' Mr Tsang said. He said customs officers were fully aware the Police Public Relations Bureau would handle inquiries and briefings on task force operations more professionally and conveniently. ''There has long been a mutual agreement and police have never forgotten to mention customs' involvement. I see no problem in that at all,'' he said. Police Narcotics Bureau chief, Chief Superintendent Keith Braithwaite, also flatly denied any clash with customs officers. ''There is none,'' he said.