SEOUL, South Korea — South Korea is offering a $50,000 reward for information about a mysterious missing billionaire who authorities say owns a ferry that sank last month, leaving more than 300 people dead or missing.

The disappearance of Yoo Byung-eun and his son has caused a media frenzy in South Korea. Yoo is a member of a church that critics call a cult and have linked to a 1987 mass suicide; church members deny involvement.

Yoo, 73, was thought to be holed up in a sprawling church compound near Seoul, and there was a tense, dayslong standoff between police and hundreds of church followers, some of whom reportedly threatened to die as martyrs.

But Yoo wasn’t there when church members on Wednesday finally opened the compound to authorities, and some speculated that he may have fled to the home of a church follower. Prosecutors and police then announced a $50,000 reward for information about Yoo’s location, and $30,000 for details about his eldest son.

Yoo, head of the now-defunct predecessor of the ferry’s current operator, Chonghaejin, allegedly still controls the company through a complex web of holding companies in which his children and close associates are large shareholders. Senior prosecutor Kim Hoe-jong said authorities believe Yoo is the chairman of Chonghaejin.

Yoo faces allegations of tax evasion, embezzlement and professional negligence.