The Consumer Council has received dozens of complaints relating to the closure of Physical Fitness and called on the gym chain to get in touch with affected customers.
The watchdog said it had received 34 complaints as of 4.30pm on Friday, involving around HK$1.9 million.
The council said it's highly concerned about the case.
Customs officers, meanwhile, said they'd received four complaints.
In an announcement, the fitness chain said it is bringing in new investors and is in talks with landlords regarding changes to leases, adding that certain branches will reopen when agreements are reached. But the Consumer Council described the follow-up arrangements as "unclear" for consumers.
A group of Physical Fitness staff was at a Labour Department office in Tai Koo to report their cases.
A senior personal trainer, surnamed Fung, said he was not surprised by the sudden closure.
“The company started delaying salary payments around eight months ago, so we [trainers] are mentally prepared for such situations,” he said. “I just did not expect the closure to happen right after the typhoon.”
Federation of Trade Unions lawmaker Aron Kwok, who was there assisting the affected workers, said they only learnt about the closure through a notice circulating online on Friday morning.
“It is for sure that the staff will not be able to receive their salary for August. They will also have to chase down their payment in lieu of notice, mandatory provident fund (MPF), annual leave, statutory holidays and severance payments,” Kwok said.
The Mandatory Provident Fund Schemes Authority said the company has not paid the MPF contributions and surcharges for about 740 employees for June and July, involving around HK$3 million.
The chairman of the Hong Kong Recreation and Sports Professionals General Union, Lee Yuet-man, said more than 700 instructors were affected by the closure of Physical Fitness.
Lee also said the fitness industry has faced significant challenges, such as staff exodus and high rents.
"During the pandemic, we all know that this shut down all the fitness centres. We estimate that we have about 30 percent of the employees change their jobs to another industry, especially going to the delivery [industry]," he told RTHK.
Lee also pointed out that many gyms moved from Hong Kong to the mainland in recent years.
As for staff, "they are trying to look for the same job in small-scale fitness centres, or maybe move to the Greater Bay Area," he added.