Hong Kong police are hunting for 10 suspected triad members wanted in connection with the murder of a gangster beaten to death during a fist fight over HK$1 million (US$128,500) in missing gambling money.

The 27-year-old victim, who was believed to have belonged to the Wo On Lok triads, met members of the Wo Shing Wo gang in a flat in a Tai Kok Tsui commercial building in the early hours of June 26, according to the force. The victim rented the space to work out, including boxing with friends.

The victim was taken to Kwong Wah Hospital in Yau Ma Tei.

The victim had been helping the Wo Shing Wo triads run their illegal gambling and debt collection business but was accused of stealing HK$1 million in proceeds, a police source said.

They agreed to settle the matter through a “free fight” – a contest where the accused takes on each member of the other gang in turn and must beat him into submission, with no weapons allowed.

“The investigation suggested the victim was given the free fight to settle [the theft] if he could beat the gang members one by one,” the insider said.

But after about an hour, the victim finally succumbed to the blows and fell unconscious.

Surveillance camera footage showed three gang members taking him to Kwong Wah Hospital in Yau Ma Tei by taxi at around 9.30am that day. Medical staff examining him found the multiple bruises and head trauma deeply suspicious and called police.

Officers from the Yau Tsim district crime squad went to the flat and found it empty but noticed a strong smell of antiseptic.

“No blood stain was found in the premises,” the source said. “We believe the flat had been cleaned.”

After checking surveillance camera footage, police arrested two men, aged 21 and 24, on June 29 and 30. One was charged with a single count of wounding with intent and the case was mentioned at Kowloon City Court on July 3. He was remanded in custody.

According to the force, the other suspect was released on bail pending further investigation.

But the case was reclassified as murder when the victim died in hospital at 11.59am on August 4. An autopsy will be carried out.

Detectives from the Kowloon West regional crime unit are now handling the case.

According to official statistics, police handled 810 reports of triad-related crimes in the first six months of this year, up 8.3 per cent from 748 in the same period the year before.