TAIPEI,  (Xinhua) -- One more person tested positive for the novel coronavirus disease (COVID-19) in the outbreak involving three naval vessels, Taiwan's epidemic monitoring agency said Saturday.

The total number of naval service personnel and cadets who contracted COVID-19 increased to 31, the agency said in a press release.

The latest patient, a cadet in his 20s, tested negative of the virus in his first COVID-19 test on April 18 but positive of certain antibodies in the blood, which led to a second test on April 24, the statement said.

The fleet of three naval vessels, with more than 700 people on board, returned to Taiwan on April 15 after a short stop at Palau from March 12 to 15 and nearly 30 days at sea. A majority of people on board disembarked before the first three tested positive with the virus on April 18.

Authorities identified over 1,800 people having contact with the patients and put 534 of them under quarantine at their residences, the statement said.

The total number of COVID-19 patients in Taiwan has risen to 429, 275 of whom have recovered and six died.  ■