SEOUL, South Korea (AP) — The South Korean government on Tuesday was looking into U.S. media reports saying North Korean leader Kim Jong Un was in fragile condition after surgery.

Officials from South Korea’s Unification Ministry and National Intelligence Service said they couldn’t immediately confirm the report. CNN cited an anonymous U.S. official who said Kim was in “grave danger” after an unspecified surgery.

The Unification Ministry, which deals with inter-Korean affairs, said it couldn’t confirm another report by Daily NK, which cited anonymous sources to report that Kim was recovering from heart surgery in the capital Pyongyang and that his condition was improving.

Speculation about Kim’s health was raised after he missed the celebration of his late grandfather and state founder Kim Il Sung on April 15.