A Norwegian cruise ship has been denied permission to dock in Mauritius over fears of a potential cholera outbreak on board.

Local authorities on Sunday denied permission for the Norwegian Dawn vessel, which has 2,184 passengers and 1,026 crew on board, to access the Mauritius capital of Port Louis, citing “potential health risks.”

The ship was on a 12-day itinerary from Cape Town, South Africa to Port Louis that started on Feb. 13.

The Mauritius Ports Authority said Sunday that samples were taken from at least 15 passengers on board. These passengers had been placed in isolation on board the vessel “due to the state of their health,” the port authority said, according to a Google translation.

“As the test results will only be known in approximately 48 hours, passengers who were due to board the ‘Norwegian Dawn’ and begin their cruise from Mauritius today will not be able to do so due to potential health risks. They will have to be relocated to available hotel establishments,” the port authority said.

A spokesperson for the U.S.-headquartered Norwegian Cruise Line Holdings said Sunday that “a small number of guests experienced mild symptoms of a stomach-related illness” during Norwegian Dawn’s South Africa voyage.

On returning to Port Louis, the spokesperson said the vessel’s management team met with local authorities to confirm that precautionary measures were being taken to ensure the wellbeing of those on board.

Multiple media outlets reported the stomach illness on board the ship was suspected to be cholera.

“The health and safety of our guests, crew and the destinations we visit is our top priority. We operate at the highest public health and sanitation standards, and encourage our guests to practice good hygiene and to report any illness-related symptoms to the onboard medical team immediately,” the spokesperson for Norwegian Cruise Line Holdings said.

“Additionally, we have elevated our sanitation procedures aboard the ship as part of our routine measures to ensure a safe environment for all on board and will continue to take any necessary measures to protect our guests, crew and destinations we visit,” they added.

The World Health Organization says cholera is an “extremely virulent” disease transmitted through the ingestion of contaminated food or water.

It is rare in the U.S., and infection is often mild or without symptoms, but the Centers for Disease Control and Prevention has warned that symptoms can also be severe. The CDC says cholera symptoms can include diarrhea, vomiting and leg cramps.

Since January last year, the U.N. says that roughly 188,000 cholera cases have been reported across eight southern African countries, including 3,000 related deaths.

Norway is poised to become one of the first countries in the world to approve the controversial practice of deep-sea mining.

In a parliamentary vote on Tuesday, lawmakers in the northern European country are expected to approve the government’s proposal to open Norwegian waters for commercial-scale deep-sea mining.

The vote is expected to pass smoothly after the government’s plans received cross-party support late last year.

Advocates say removing metals and minerals from the ocean’s seabed is necessary to facilitate a global transition away from fossil fuels, adding that the practice is less environmentally damaging than land-based mining.

Critics say deep-sea mining is “extremely destructive,” while scientists warn the full environmental impacts are hard to predict.

Critical minerals such as cobalt, nickel, copper and manganese can be found in potato-sized nodules at the bottom of the seafloor. These minerals are used for electric vehicle batteries, wind turbines and solar panels.

The Environmental Justice Foundation, an international NGO, says the bottom line is that any possible benefits from deep-sea mining “do not outweigh the environmental and economic risks.”

Norway’s proposal paves the way for companies to apply to mine for critical minerals in its national waters near the Svalbard archipelago. The area, which is part of Norway’s extended seabed shelf, is estimated to be larger than the U.K. at roughly 280,000 square kilometers (108,108 square miles).

Norway’s government does not intend to immediately start drilling for critical minerals, if the plan is approved. Instead, companies will need to submit proposals for licenses that will be voted on a case-by-case basis in parliament.

The approval of deep-sea mining would put Norway at odds with both the U.K. and the European Commission, the EU’s executive arm, which have pushed for a temporary ban on environmental concerns.

The Norway Environment Agency has previously criticized the government’s impact assessment of the plan, while 120 EU lawmakers wrote an open letter in November calling on the country’s parliament to reject the project.

The letter from EU lawmakers also warned about the risk that the proposal posed for marine biodiversity, the acceleration of climate change and for traditional activities, such as fisheries.

In a separate open letter calling for a pause to deep-sea mining, more than 800 marine science and policy experts across the globe warned that very little is known about deep-sea habitats and biodiversity.

They say that more robust research is necessary to better understand what’s at stake.

“The sheer importance of the ocean to our planet and people, and the risk of large-scale and permanent loss of biodiversity, ecosystems, and ecosystem functions, necessitates a pause of all efforts to begin mining of the deep sea,” the letter says.