The Ocean Amazing was scheduled to arrive at a port in the southern province to deliver cargo, but on Feb. 20, after it entered Vietnamese waters, a sailor died on the ship due to an unidentified non-health-related issue.

Vung Tau authorities then tested the remaining 20 sailors on board for the novel coronavirus. At least five of them have tested positive, the Ba Ria-Vung Tau Province Center for Disease Control said.

"All the sailors are Indonesian, and most do not have symptoms of Covid-19," a source said.

Gene sequencing is being performed on their samples and a second test is underway. If it too returns positive, the ship will be sent back to Indonesia for replacing the crew and disinfection before it can return to Vietnam with the cargo.

As of Wednesday morning the sailors were still on the ship anchored at sea, and have not carried out procedures to enter Vietnam.

Vietnam has had 2,403 Covid-19 cases so far, 604 still active.