Jin-on, leader of male group F.cuz, was hospitalized Thursday after suffering an acute stomach pain during the rehearsal of M Countdown, a music program on Mnet. Doctors at first thought he had appendicitis, but after more tests it was revealed that he had diverticulitis, a common digestive disease usually found in the large intestine. The most prominent symptom of the disease is abdominal pain, but nausea or vomiting could occur when infection grows more severe.

F.cuz had to appear on M Countdown only with three members, because the program was aired live. The group’s remaining schedule for this week will be cancelled. The agency representing F.cuz said that doctors haven’t decided on surgery yet and apologized to the fans for the missed appearances. F.cuz had released a mini album last Thursday and its title song “No One” was steadily gaining popularity.