Detectives investigating a Wan Chai bar brawl involving five off-duty senior expatriate police officers are expected to send an inspector to South Korea in search of photographs taken on the night of the incident. It is understood that an inspector from Hong Kong Island Regional Crime Unit has either left or is about to leave for Seoul to find a customer who was in the Devil's Advocate bar in Lockhart Road at the time. Police sources say investigators want to interview a Korean man who is believed to have taken the photographs when trouble flared shortly after 5am on Saturday, February 3. Michael Armstrong, 35, Assistant Divisional Commander for Castle Peak, needed hospital treatment after he was hit over the head with a bottle outside the bar. Two men - Oluwaenia Olusanmokun, 20, the son of Nigerian Consul-General Ebenezer Olusanmokun, and an unidentified Dutch-Filipino man, aged 19 - were arrested in connection with the incident. Both men have been released on $1,000 police bail and have to report back to police on April 4. A stun-gun was also seized in connection with the incident. 'A customer in the bar took some photographs either during and/or after the incident and his details were taken. An inspector from the regional crime unit is due to be sent to Korea to get the pictures,' a police source said. The move has raised questions about the cost of the trip - a round-trip ticket to Seoul would cost about $3,000 - but it is understood detectives are hoping the Korean man will also agree to give a statement. Last night the force's Director of Operations, Senior Assistant Commissioner of Police Ng Wai-kit said he was unaware of the trip but added: 'I am not directly in charge of the investigation so I cannot answer the question. Even if I did know, I would have to consider whether giving out information would prejudice an ongoing investigation.' As well as a normal criminal inquiry, force bosses have ordered an internal investigation into the incident because it involved senior officers. A report on the internal investigation, also carried out by Hong Kong Island Regional Crime Unit - will be sent to Mr Ng as head of police operations. The South China Morning Post has been told that as well as Mr Armstrong, the following officers were in the bar at, or around, the time of the incident: David Williams, Senior Inspector of the Organised Crime and Triad Bureau; Peter Burbidge-King, District Commander of Kowloon City; David Cameron, Assistant District Commander of Kowloon City; and Ian Seabourne, Deputy Regional Commander of Kowloon West. It is understood a number of the officers have given statements to detectives working on the case. Before the incident, the off-duty officers had been celebrating the 18th-century Scottish poet Robert Burns at police headquarters in Arsenal Street. 'Burns Night' celebrations are usually held around the end of January.