SINGAPORE (REUTERS) — A passenger who tested positive for COVID-19 aboard a ‘cruise-to-nowhere’ from Singapore, forcing the ship to return to dock and nearly 1,700 guests to isolate, has been found not to have the virus, Singapore’s health ministry said on Thursday.

Passengers on Royal Caribbean’s Quantum of the Seas vessel were held in their cabins for more than 16 hours on Wednesday after an 83-year old man tested positive for COVID-19 after he came to the ship’s medical center with diarrhea.

When the ship returned to port on Wednesday, the passenger was taken to hospital where he took two further tests which did not reveal infection. A third negative test on Thursday led authorities to declare him virus free.

“A final confirmatory test … has confirmed that the 83 year-old male Singaporean…does not have COVID-19 infection,” the health ministry said in a statement.

Royal Caribbean did not immediately respond to a request for comment.

The cruises, which sail in waters off Singapore, are open only to Singapore residents and make no stops, and are part of the island state’s effort to revive a tourism industry which has been battered by the pandemic.

The resumption of Royal Caribbean’s so-called ‘cruises-to-nowhere’ last week were its first sailings since the Miami-based company halted global operations in March due to the pandemic.

Precautions for the cruises involved pre-departure testing and for guests to carry an electronic contact tracing device, wear masks and social distance at all times.

Editing by Tom Hogue & Simon Cameron-Moore