South Korean officials say it remains unclear what is behind the trend, with epidemiological investigations still under way.

韩国官员表示，韩国尚不清楚这一趋势（出现复阳病例）背后的原因，流行病学调查仍在进行中。

An epidemiological investigation that started on Saturday has combed through all the close contacts of the new cases.

周六开始的流行病学调查排查了新增患者的所有密切接触者。