Two Hong Kong construction chiefs charged with manslaughter over the deaths of two workers caught in an underground chamber filled with toxic gas have been released on bail after almost nine months on remand.

Shum Yuk-kuen, 62, a director of Shum Development, a subcontractor at the construction site, and Yip Lai-pan, 40, the project manager for main contractor Raft (E&M) Engineering, were granted bail on Wednesday after they appeared at Kowloon City Court for a fifth hearing.

The pair are charged with “unlawfully killing” Lau Ho-cheong, 63, and Kwok For-kee, 61, who were working in an underground chamber at the Lyric Theatre Complex at 1 Austin Road West in the Kowloon West Cultural District between September 23 and 24 last year.

The bodies of the victims were discovered after they had been trapped in the hydrogen sulphide-filled underground tube for more than 12 hours.

Railway operator the MTR Corporation said at the time that the two men were repairing seawater cooling pipes linked to the air-conditioning system at the nearby Elements shopping centre, which it developed and manages.

The prosecution told the court that a new expert report was submitted to the Department of Justice after the last adjournment which outlined the concentration of hydrogen sulphide – known as “sewer gas” and which has a characteristic smell of rotten eggs – needed to kill.

The prosecution added that a separate report had found the times of death of the two workers were hours apart.

It said the department would need more time to analyse the new evidence, which involved a significant amount of scientific information, and that a three-month adjournment was needed.

The scene at the West Kowloon Cultural District construction site in Austin Road after two construction workers were found dead. Photo: Yik Yeung-man

Defence lawyers asked the court to consider bail for the defendants, who had been on remand.

Magistrate Kestrel Lam Tsz-hong highlighted that the prosecution had asked for several adjournments after the two defendants made their first appearance in court last September.

“Although the case is complicated and involved a lot of data collection, the defendants, however, have been remanded for quite a while,” Lam said. “There is still a long way to go before the case goes to trial.”

Lam released Shum on HK$100,000 (US$12,805) bail, with his son guaranteeing the same amount as a surety.

Yip was released on HK$130,000 bail, with a surety of the same amount provided by his sister.

The two were ordered to surrender their passports, remain in Hong Kong and report to police three times a week.

They were also told not to spend a night anywhere other than at their home addresses.

The case was adjourned until September 13.