The public prosecution service is investigating possible human trafficking and people smuggling at Amsterdam gym chain Saints & Stars, after reports that dozens of cleaners from the Philippines and Indonesia were being exploited, the Parool reported on Wednesday.

A department spokeswoman told the paper a criminal investigation is under way but declined to say who or how many people are officially suspects. The police are currently interviewing cleaners as part of the inquiry, the Parool said.

The paper said at the end of July that up to 23 cleaners had been forced to work up to 17 hours a day and share beds with strangers .

The workers were also made to surrender their passports while the company organised their visas and work permits but failed to do so, the paper said. Many were recruited directly in their home countries.

The company has denied any wrongdoing and the managers responsible for cleaning the gyms have been suspended.

The Philippines’ ministry of labour migration has also started its own investigation into the exploitation of cleaners at the gym’s four branches in Amsterdam.