South Korea's forensic agency says it cannot determine the cause of death for the fugitive tycoon blamed for the recent ferry disaster.
Last week police identified a body found on June 12 as Yoo Byung-eun.
Yoo was wanted for questioning on possible charges linked to the sinking of the Sewol ferry in April, which killed more than 300 people.
Forensic experts said the state of the body meant the manner of his death could not be determined.
"It was impossible to conclude the cause of death since Yoo's body was in a very advanced stage of decomposition," Seo Joong-seok, director of the National Forensic Service (NFS), told journalists.
The NFS had ruled out drugs or poison, he said. But there had been no way to rule out other possible causes.
Police have been criticised for failing to connect the body, which spent six weeks in the mortuary, with Yoo, who was the subject of a lengthy manhunt.
Prosecutors have revealed that he hid in a cupboard at his holiday home to evade arrest. His body was found just 2.5km from his cabin, in a plum orchard.
Yoo owned Chonghaejin Marine Co, which operated the Sewol.
It sank on April 16 off Jeju island, killing most of its passengers including scores of high-school students. Investigators say it had been illegally modified to carry more passengers and cargo, and was overloaded.
Yoo was wanted for questioning on possible charges of embezzlement and criminal negligence.
The sinking of the Sewol triggered widespread grief and anger at the government, which has promised to overhaul its bureaucracy and improve its emergency response.
Two separate trials - one for the vessel's captain and crew, and another for officials at Chonghaejin Marine - began last month.