But neither the MTR Corporation nor the government addressed how the deaths seemingly went unnoticed overnight.
The Labour Department said it would complete an investigation as soon as possible to identify the cause of the deaths and determine the liability of the parties involved.
But a spokesman for the department refused to disclose the names of the contractors.
The MTR Corp said it would provide HK$100,000 (US$13,000) to each of the families of the deceased workers. It also revealed the contractors involved would jointly pay a total of HK$200,000 to each family.
According to the rail giant, the two men were repairing seawater cooling pipes linked to the air-conditioning system of the neighbouring Elements shopping centre. The mall was developed and run by the MTR Corp.
Police and firefighters found the two victims unconscious at the underground site in the West Kowloon Cultural District after receiving a report at 7.30am on Sunday from construction workers saying the pair had not left the area since Saturday.
The men were then taken to Queen Elizabeth Hospital in Yau Ma Tei, where they were declared dead.
After rushing to the hospital to identify the body of his father, a man surnamed Lau began pressing authorities to explain how the disappearance went unnoticed overnight.
“Where had the supervisors gone when two workers were still in a closed area?” he told local media.
“If it was not for the [family of the other victim] who called the supervisor, I wouldn’t have known my father was involved in an accident.
“I made plans to have yum cha with him [on Sunday] to celebrate the Mid-Autumn Festival. I want to know why this happened.”
The wife of the other victim, surnamed Kwok, said her husband had been doing drainage works under a contractor for more than a decade.
Fay Siu Sin-man, who chairs the Association for the Rights of Industrial Accident Victims, said she was told by families of the deceased they were supposed to end work at 5pm on Saturday and were expected to reach home by 7pm.
“They asked around and tried contacting the supervisor last night but the phone call went unanswered. The other family only knew about the tragedy when police knocked on their door this morning,” she said.
Siu also told the Post it was her understanding that Raft (E&M) Engineering was responsible for the air-conditioning project.
Both the MTR Corp and the government have so far refused to confirm the speculation.
The Post has reached out to Raft (E&M) Engineering for comment.
The company is listed as a contractor on the rail giant’s website for a HK$9.5 million three-year tender awarded in February 2020 for maintenance services for mechanical ventilation and air-conditioning systems at the Elements shopping centre.
The rail giant said it had employed an “air-conditioning contractor” for the project and was working with the company to gather details about the incident.
It pledged to fully cooperate with the investigation by relevant government departments.
Firefighters were deployed to search for the two near a 200-metre-long (656 feet) pipe. The area was filled with a strong odour when they arrived at the scene.
Rescuers found the two victims six metres below the ground, between the 100 and 200-metre mark of the pipe.
They said rescue efforts were challenging as they also had to pump gas out of the pipe. Eight fire trucks and two ambulances were sent to the 20-by-20-metre area of the construction site where the men were found.
Local media reported that a high concentration of hydrogen sulphide was suspected to be present in the underground area.
Hydrogen sulphide is a commonly occurring component in biogas. It is known for its distinct odour resembling that of rotten eggs and can pool and stagnate in wells and poorly ventilated areas because of its higher density compared with the surrounding air.
Two industry experts told the Post that accidents involving staff members carrying out underground works should not go unnoticed under existing protocol.
Wong King, a former president of the Hong Kong Institute of Utility Specialists and an engineer, explained that contractors were required to keep detailed logs, in the form of a certificate, recording the movements of labourers involved in underground works.
Such details included the time of entry and expected departure from the site, name of the staff member responsible for monitoring colleagues underground and identity of person who signed off on the relevant work permit.
“All items on the certificate have to be recorded, with related personnel having undergone adequate training,” Wong said.
Asked about why there could have been a high concentration of hydrogen sulphide at the site, Wong said he suspected a possible leakage nearby. He explained utility tunnels, an underground environment designed to carry utility pipes, should not contain contaminated water.
Lee Kwong-sing, a safety adviser with the Hong Kong Construction Industry Employees General Union, said hydrogen sulphide, which occurred naturally in drains, was very toxic even in low concentrations and could not be filtered out by gas masks.
He said workers heading underground were usually equipped with breathing apparatus such as oxygen tanks and a safety harness that connected them with another staff member above ground.
“The rope allows those above ground to pull them to safety or for rescuers to locate them easily. They should also be carrying a personal alarm when they are in an enclosed underground area, which is set off if workers are unresponsive after 30 seconds,” he said.
Department guidelines state that the concentration of hydrogen sulphide should be lower than 10 parts per million and employers must ventilate underground sites to dilute any toxic gases.
The city saw a surge in fatal industrial accidents in August, including a single Saturday where three workers died in separate accidents.
Thirteen fatalities were reported in the construction industry in the first quarter of this year, almost double the seven cases for the same period in 2022.
Three workers died after inhaling hydrogen sulphide and drowning at a CLP Power work site in 2017, following a sudden flooding of sewage into a hand-dug tunnel five metres below ground.
Contractor Kum Shing Construction was fined HK$11,000, with two of its subcontractors fined HK$6,000 in the incident over minor negligence charges, as they were cleared of failing to provide a safe workplace.