TOKYO — Since 2013, more than 175 abandoned ships have been found floating off the coast of Japan, with scores of unidentified bodies.

Most of the ships and the dead are believed to have come from North Korea. But what happened to these ships, what happened on board to the crew, and why have 10 ships and 23 bodies been found within just the last two months?

The bodies are often severely decomposed and documents or photos that would help identify the deceased are sorely lacking. Japanese officials are investigating but there are no clear answers, although there are reasonable theories to explain the phenomenon.

On Wednesday, the Japanese Coast Guard discovered an unidentified body in an abandoned fishing ship off the coast of Niigata Prefecture's Sado City, in the Sea of Japan. The ship had been found on Nov. 14 but was only successfully taken out of the water and inspected yesterday. According the Coast Guard, they received word from the Sado City Fishermen’s Association that a strange ship was floating in the harbor last month.

The wooden ship, 45 feet long, was found capsized; its hull blackened and discolored. There was Korean writing (hangul) and what appeared to be numbers on the body of the ship as well.

The rough ocean conditions made entering the ship impossible and the Coast Guard only succeeded in raising the boat on Wednesday afternoon. Upon searching the ship, they found fishing equipment. The dead man inside was wearing a black sweater and slacks and an orange life vest; his head was partially skeletonized. He is believed to have died within the last three to four months.

The Japanese Coast Guard announced that since October, there have been 10 wooden ships found abandoned and floating off the coasts of Japan, ranging from Hokkaido in the North to Fukui Prefecture in the Chubu region. From these 10 ships, 24 bodies have been recovered, all male.

Most of the men are believed to have died within the last four months.

Because of the fragments of Korean writing found on the ships and the life vests, the primitive structure of the vessels, and the particular fishing equipment found aboard, the Japanese authorities and most experts believe the majority of the ships are from North Korea.

The first of the ships was found around Oct. 27 . On Nov. 20 , three boats were found adrift near the city of Wajima, which is on the west coast of Japan. One of the boats contained 10 bodies, already heavily decomposed, and had written on its hull in hangul, “Korean’s People Army,” the proper name of the North Korea military forces. There were also pieces of what appeared to be a North Korean flag.

Was it a failed spy mission? A boat full of defectors?

Neither answer seems likely.

A few days later on Nov. 22, near the coast of Fukui Prefecture, another wooden fishing vessel was found with seven bodies inside. Four of the bodies were partly skeletons, with some skulls having been detached from the remains, probably due to decomposition rather than a deliberate amputation.

The surge in the appearance of these deadly ghost ships may be due to the plans of the Great Leader gone off-course.

Kim Jong-Un, has been visiting fishery stations in North Korea since this summer and reportedly ordered the military and civilian populace to increase the production of marine products.

Satoru Miyamoto, an associate professor of Seigakuin University, who is an expert on North Korean affairs, told Japanese public broadcaster NHK, “In North Korea, all companies exist under the auspices of either the government, the party or the military. These ships all appear to be fishing vessels under military control. The drive by Kim Jong-Un to raise the fishing haul probably resulted in many poorly prepared vessels going out to sea.”

NHK reported on Nov. 25 that, since 2013, there have been a total of 175 abandoned ships that have floated into the waters surrounding Japan, which are believed to be from North Korea.

Hidenori Sakanaka, former chief of the Tokyo Immigration Bureau, who now runs a nonprofit group promoting immigration to Japan, told The Daily Beast that North Korean ships running adrift in Japan had been happening for years.

“It’s possible that some of the ships that came here were people seeking to escape the oppressive North Korean regime, but seems unlikely.”

The last time North Korean defectors reached Japan was in 2011.

On Sept. 13, 2011, the Japanese Coast Guard found and rescued a small wooden ship, about 26 feet in length, off the coast of Wajima. The six adults and three children aboard were briefly given refuge in Japan and were then transported to South Korea.

Diplomatic relations between Japan and North Korea are particularly strained due to unresolved abduction issues.

During the 1970s and 1980s, the North Korean government abducted at least 17 Japanese citizens, primarily to train North Korean spies.

While some of the abductees were allowed to return to Japan, the Japanese government feels that North Korea is still holding many others hostage and has not clarified the fates of suspected abductees.