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Fourteen Americans who were among the hundreds of people evacuated from a quarantined cruise ship off Yokohama, Japan, on Sunday have tested positive for the novel coronavirus that has claimed nearly 1,800 lives in a growing outbreak in China.

More than 300 U.S. citizens and their immediate family members who had been passengers on the Diamond Princess cruise ship were taken off the vessel and repatriated back to the United States on two chartered flights that landed at Travis Air Force Base, California, and Lackland Air Force Base, Texas, early Monday.

In a statement, a State Department spokesperson said Monday that the American evacuees were all deemed asymptomatic and fit to fly before being processed for evacuation.

But during the evacuation process, after passengers had left the ship and gone to the airport, U.S. officials received notice that 14 passengers, who had been tested two to three days earlier, had tested positive for COVID-19, the disease caused by the novel coronavirus.

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"These individuals were moved in the most expeditious and safe manner to a specialized containment area on the evacuation aircraft to isolate them in accordance with standard protocols," the spokesperson said.

The State Department made the decision to allow the 14 individuals, who were in isolation, separated from other passengers and who continued to be asymptomatic, to remain on the aircraft to complete the evacuation process after a consultation with health officials, according to the statement.

U.S. passengers who have chosen to leave the Diamond Princess cruise ship, are transported by shuttle bus to Haneda airport to fly back to the United States on Monday, Feb. 17, 2020. Philip and Gay Courter via Reuters

The Diamond Princess has been on quarantine since Feb. 3 after a man who disembarked in Hong Kong was diagnosed with the virus.

The outbreak continued to grow Monday as the death toll rose to 1,772 and the number of confirmed cases reached 70,635 in China.

Dr. Tedros Adhanom Ghebreyesus, the director-general of WHO, said that outside of China, the organization had received reports of 694 cases in 25 countries, including three deaths.

Japan's health ministry confirmed 99 additional coronavirus cases on board the ship Monday. More than 1,700 people on the Diamond Princess, which had 3,700 passengers and crew on board, have been tested since the quarantine began — 454 of them have tested positive for the virus, including some Americans.

The State Department said all evacuated American passengers were closely monitored by medical professionals throughout the flight and any who become symptomatic were to be moved to a specialized containment area.

The evacuees will now be placed under mandatory quarantine for 14 days.

"Passengers that develop symptoms in flight and those with positive test results will remain isolated on the flights and will be transported to an appropriate location for continued isolation and care," the spokesperson said, without elaborating on where that location could be.

Hundreds of Americans were evacuated from Wuhan, the center of the epidemic in China's Hubei province, aboard chartered flights in late January and earlier this month. They were also subjected to a mandatory 14-day quarantine at military bases upon arrival in the U.S.

Canada, Australia, Hong Kong and Italy are also making efforts to evacuate their citizens from the quarantined cruise ship.