South Korean forensic investigators said on Friday that they were unable to determine the cause of death of Yoo Byung-eun, the fugitive shipping tycoon whose company operated the Sewol ferry that sank in April, killing more than 300 people.

The forensic team reportedly said that it had conducted additional tests on Yoo's body, which was reportedly found on June 12 in a field in Suncheon, a city located 186 miles south of Seoul, but failed to detect the exact cause of death because the body was badly decomposed. Police said Tuesday that they could only identify the body from the results of DNA and fingerprints tests done by the National Forensic Service.

"We are aware there are many questions and did our best, but it was impossible to determine the cause of death," Lee Han-young, a senior official at the forensic agency, said, according to Reuters. "It is possible in some cases involving decomposed bodies to determine the cause of death but, in Yoo Byung-un's case, there was simply too much tissue damage so it was difficult to find leads that can determine the cause of death."

Forensic chief Seo Joongseok and other forensic doctors reportedly said that they did not find any evidence that showed the 73-year-old was poisoned or had received an external trauma. Police officials also reportedly said that there was no evidence of foul play so far in Yoo's death.

Although the autopsy report stated that there was no evidence of injury from a weapon, the tissues in the head and neck had been damaged after being badly decomposed, Reuters reported.

A massive manhunt was launched to find the businessman, who went missing shortly after the Sewol, which was carrying more than 470 people, mostly school students, to Jeju island, about 60 miles south of the Korean peninsula, sank on April 16, in what became one of South Korea's deadliest maritime disasters in decades.

Authorities have reportedly faced public criticism over their delay in determining the identity of Yoo's body, which was found more than a month ago.

The ferry disaster triggered massive outrage across the country over the handling of the sinking.

The 15 surviving crew members of the ferry, including the captain, are currently on trial on negligence and homicide charges. The incident also led President Park Geun-hye to replace seven ministers in her cabinet, the first reshuffle since she took office in February 2013.