Nearly one out of three COVID-19 cases reported in the past two weeks had an unknown transmission source.

According to the Korea Disease Control and Prevention Agency(KDCA) on Thursday, the routes of infection for 29 percent of two-thousand-629 new cases reported over the past two weeks remain untraceable. 

It is the highest to be posted since April last year when quarantine authorities began to compile related data.  

The percentage of COVID-19 cases with unknown routes had been on a slight downturn after surging a little over 28 percent last Tuesday.