Japanese authorities were investigating a serious of mysterious boats including some carrying decaying bodies that were found drifting at sea in recent weeks. A total 11 wooden vessels, some rickety and in poor conditions, have been washed ashore or retrieved by the coastguard off the country's western coast over the past two months.

The lifeless bodies of 25 people were found on board, authorities said as they were trying to ascertain where the boats came from. Early evidence suggested the vessels had crossed the Sea of Sea from the secretive North Korea.

Coastguard spokesman Yoshiaki Hiroto said that Korean writing was found on the boats. "We are carrying out an investigation into these vessels and where they come from, although reports that Hangul characters were on the boats are correct," Hiroto told UPI new agency.

Finishing gear was also found, while a boat reportedly bore the inscription "Korean People's Army No. 325" on the hull. Speculations were rampant as to who were the people on board. The most credited option was they were fishermen that ran into trouble at sea and later perished after a prolonged exposure to the elements.

Another theory was that the passengers were North Korean defectors that similarly became stranded at sea while attempting to flee the regime for South Korea or Japan. In a similar incident five decomposing bodies were found aboard a stray vessel by Japanese authorities in 2012.