Seven people with triad backgrounds were arrested on suspicion of murder and preventing the lawful burial of a body after a corpse was discovered at a construction site for the Hong Kong-Zhuhai-Macau bridge earlier this month.

Five men aged between 39 and 59 and two women aged 24 and 48 were arrested in different districts including Hung Hom and Mong Kok in Kowloon, Tuen Mun in the New Territories and Aberdeen on Hong Kong Island on Sunday, Apple Daily reported.

One of the female suspects is a South Asian and the rest are local, it said, but both the suspects and the victim were all drug users.

Police took two of the suspects to a flat on 165 Tung Choi Street in Mong Kok where officers believed the victim was killed before being wrapped in layers of plastic bags and dumped at the East Coast Road construction site near Hong Kong International Airport on Lantau Island.

The dead body was found on May 4 by a construction worker.

Officers believe that the murder took place in late February to early March when the victim, a 30-year-old man surnamed Siu, who was out of jail a few months and had a significant criminal record, had a dispute over drugs with other suspects, Oriental Daily reported.

Acting superintendent Tse Tan-san said two injuries found on the back of Siu’s head might have been caused by a blunt object. They believe that the seven suspects did not attack the man at the same time but are still investigating their possible roles.

Police have not yet found a murder weapon, and an autopsy will be needed to determine the exact cause of death.

Meanwhile, officers are hunting a Pakistani man who believed to have transported the corpse.

Police did not rule out the possibility of making more arrests.