The band called off its Daegu gig at the last minute to allow Levine to deal with "health problems", and the singer has since posted a shot of himself wearing a neck brace on Instagram.com.
He added the message, "Hey guys sorry we had to reschedule... See you Thursday!" prompting online speculation about his ailments including one rumour that suggested Levine had been involved in a car crash.
Concert promoters were quick to dismiss the story, insisting Levine was suffering "neck muscle issues" and was told to rest.
A spokesman for Live Nation Korea says, "The artists and staff tried very hard to prepare for (the concert) until the day before on Friday, but it seemed problematic to proceed with the show given vocalist Adam Levine's neck muscle issues."
Saturday night's concert has been rescheduled to 10 September (15) and South Korean shows in Seoul on Monday (07Sep15) and Wednesday (09Sep15) are scheduled to go ahead as planned.