A coronavirus outbreak on one of Taiwan’s navy ships has raised concerns that a re-infection could threaten one of the world’s success stories in the fight against the pandemic.

Twenty-seven sailors on a navy supply vessel were confirmed to have the virus shortly after it returned from a visit to Palau earlier this month. Taiwan’s defense minister apologized Tuesday night and said he was willing to resign if requested to do so by the island’s president, Tsai Ing-wen.

Tsai apologized at a briefing Wednesday, saying Taiwan is investigating the outbreak on the ship, and that the president should take responsibility. She said the navy ship was on an annual routine drill and "special” mission, which she didn’t specify, and only visited Palau.