BUENOS AIRES: Argentina is trying to solve the mystery revolving around a crew of 57 sailors who were tested negative before setting the sail, but when they returned after 35 days they were tested positive for COVID-19.

The health ministry for the southern Tierra del Fuego province said the Echizen Maru fishing trawler returned to shore after some of the crew members showed symptoms of the viral infection.

The health ministry said that 57 of the 61 crew members were tested positive for coronavirus in new tests. It said they did not have the disease when they were embarking on the voyage. They all had undergone 14 days of mandatory quarantine at a hotel in Ushuaia.

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Two of them have tested negative for the virus, while results of two others are awaited, AFP news agency reported.

“It’s hard to establish how this crew was infected, considering that for 35 days, they had no contact with dry land and that supplies were only brought in from the port of Ushuaia,” said Alejandra Alfaro, the director of primary health care in Tierra del Fuego.

“The chronology of symptoms in the crew to establish the chronology of contagion is being examined by a team,” she said.

The head of the infectious diseases department at Ushuaia Regional Hospital, Leandro Ballatore, said “It is the case that escapes all description in publications, because an incubation period this long has not been described anywhere. We cannot yet explain how the symptoms appeared.

More than 100,000 infection cases and over 1860 deaths have been reported so far in Argentina.