This wanted poster for deceased billionaire Yoo Byung-eun was released in May. Pic: AP.

SEOUL, South Korea (AP) — South Korea’s state-run forensic lab says it has failed to find out how a fugitive billionaire blamed for April’s ferry disaster died.

Police said earlier this week that a badly decomposed body found in a rural area last month was identified as Yoo Byung-eun. Authorities had sought the 73-year-old, believing he owned the sunken ferry and that his alleged corruption may have contributed to the disaster.

(MORE: Bereaved families clash with police at Sewol tragedy anniversary event)

The state-run National Forensic Service said Friday that Yoo’s body was decayed too much to discover the exact cause of death.

Agency forensic doctors say they did not find any evidence showing that Yoo was poisoned, suffocated or died of external pressures.

The sinking left more than 300 people dead, mostly high school students.

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