Taiwanese authorities are trying to track down thousands of people who might have come into contact with more than 700 sailors who were allowed to disembark after a “goodwill” mission to the Pacific Islands, despite several reporting fevers and respiratory problems while on board.

So far 27 sailors have been diagnosed with Covid-19, prompting accusations of “serious lapses” in a country which has been internationally lauded for its successful virus response.

Taiwan has recorded fewer than 430 cases since the outbreak began. Last week it was celebrating three days with no new cases, with buildings in Taipei lit up with the word “zero”.

Then on Saturday health officials announced three new diagnoses of Covid-19. All were military personnel from the supply ship Panshi which was sent on a “goodwill” mission to the Pacific Island nation of Palau. On Sunday they added 22 cases – including 21 from the ship. On Monday, another three.

More than 700 sailors from the mission have now been recalled into quarantine and authorities have contacted more than 200,000 Taiwanese people by text message, to alert anyone who may have been in contact with them after the ship was disembarked.

The ship stopped at Palau – one of just 15 countries which recognise Taiwan as an independent nation – for three days in mid-March. Palau’s government says they still have no cases in the country, making it unlikely the sailors picked up the virus there.

It returned to port on 9 April, with the crew remaining on board for just six days under local quarantine requirements. Three days after everyone disembarked – without health screenings, according to the defence minister – 24 crew tested positive for the virus.

In the three days between disembarking and being recalled, it is estimated the sailors visited more than 90 locations across 10 counties, including restaurants, trains, university campuses, temples, and sport centres.

A map published by Taiwan’s centres for disease control pinpoints the known locations infected sailors visited. Markings stretch the length of the island’s west coast.

The cluster has prompted questions on why the fleet embarked on the goodwill mission during a pandemic.

The ministry of foreign affairs distanced itself from the scandal, saying the decision to go ahead with the mission was made by the navy. Ministry spokeswoman Joanne Ou said the mission was an important regular event for the military and the navy.

The South China Morning Post reported military leadership told a government meeting last week there was no health issue among the crew on board, and then retracted it this week. According to the navy 148 officers had in fact presented to the ships doctors during the 45-day mission, five with fever and 10 with respiratory problems.

Opposition legislator Wu Sz-huai accused the military of a “serious lapse in dealing with crisis”.

On Monday the defence minister, Yen Teh-fa, apologised to the people of Taiwan, the affected soldiers and their families, for approving the mission and offered to resign. Senior Navy commanders would be reassigned, he said.

“Those who should be punished will be punished,” he said.

The itinerary of the ship was not clear. Democratic Progressive party legislator, Wang Ting-yu, wrote on Facebook that the ship took 19 days to return because they stopped for “a confidential mission”.

“They were not on vacation and people shouldn’t be too harsh on the mission and the Navy,” he said.