Brazilian police say they’ve “rescued” 11 crew members working in “slave-like conditions” on board the cruise ship MSC Magnifica, noting that the employees were forced to work for up to 16 hours a day. According to a BBC report, some are also alleged to have been victims of sexual harassment.

Police stopped the ship last Tuesday at the northern port of Salvador, where it had docked with more than 3,000 passengers. Officials said the subsequent operation was the culmination of a monthlong investigation stemming from a tip-off by members of Magnifica’s crew.

Italian cruise operator MSC Cruises, which owns Magnifica, has vehemently denied the allegations that it subjected its workers to unfair conditions. “MSC Crociere is in full compliance with national and international labor regulations and is ready to cooperate with the authorities,” it said in a statement.

“After reviewing thousands of pages of documentation and conducting hundreds of interviews with crew members, Labor Ministry inspectors went on board MSC Magnifica on April 1 and alleged irregularities in the working conditions of 13 crew members, and invited them to disembark.” Two of the workers refused to leave the vessel, while the other 11 were taken to a hotel in Salvador, according to local reports.

MSC Cruises told the BBC its four ships operating in Brazilian waters had all passed intensive and repeated inspections by the Brazilian Labor Ministry in the past, adding that it had not received “any evidence or legal notification” from the Ministry.

Dr. Ross Klein, who has testified before Congress numerous times on cruise-related issues and is the author of four books, including Cruise Ship Blues: The Underside of the Cruise Ship Industry, told International Business Times last year that because they navigate through international waters, the rules governing cruise ships are decidedly murky.

“Cruise companies register their ships where the costs are lowest and the oversight and requirements are the least, which directly impacts labor issues,” he said. “A ‘flag of convenience’ also impacts whether a ship is subject to the laws of the countries it visits/operates out of, and also affects financial liability to passengers and crew.”

Today's business model began as early as the 1920s with the transition to so-called flags of convenience. A cruise liner like the Titanic would have had a crew from the nation whose flag graced the top of the ship. Now, ships registered to places like the Bahamas and Panama are the norm. By doing so, ship owners found they could skirt increased regulations and rising labor costs, while avoiding paying federal taxes to the nations out of which the ships actually operate.

Under this system, the only labor laws that would apply to a ship would be those of the nation it's registered to. In the mid-2000s, following the settlement of Borcea vs. Carnival, the cruise industry began to include arbitration clauses in cruise ship workers' contracts, making it even harder to settle grievances.

A report published in the journal Tourism Management this month alleges that cruise lines are utterly failing at corporate social responsibility to their staff, the environment and the destinations they visit. Researchers from the University of Leeds highlighted evidence dating back to 2010 of the “frequent violation of rights for disadvantaged groups, including charges for medical examinations, visas, transport and administration, putting cruise industry workers into a level of debt that cannot be repaid and is comparable to forced labor,” according to a summary of the report.

The University of Leeds study also found that cruise companies had provided little information on how they would implement new regulations ushered in by the Maritime Labor Convention last August. These new rules, created in 2006, cover a number of things like hours of work and rest, paid annual leave, onboard medical care, heath and safety protection, management of recruitment agencies and the written confirmation of contractual conditions.

Cruise Lines International Association, the largest trade organization of the cruise industry, said in a statement released last Friday that the University of Leeds report was “seriously flawed” and “deeply disappointing.”

“The cruise industry is highly regulated on an international basis to exacting standards towards both the environment and labour welfare,” it said. “In both areas we go above and beyond those high thresholds to enable our 21 million annual global customers to enjoy the seas in which they cruise and be cared and looked after by a motivated and content workforce.”