Over the past few months, more than 10 wooden boats with over 20 dead bodies have been found in the Sea of Japan or near the coast.
The bodies were badly decomposed; two were found without heads, and one boat contained six skulls, according to Japanese coast guard, indicating that the bodies had been adrift for some time.
The first boat was found in October, and the rest in late November.
One of the three boats found adrift off the city of Wajima on Nov 20 reportedly bore the characters for Korean People's Army, the name of North Korea's military defence forces.
Japanese police told Telegraph that they believe the victims were either fishermen who were unable to return to their ports in North Korea as most of the boats were carrying fishing equipment, or defectors attempting to escape the repressive regime.
Maritime expert Yoshihiko Yamada told Japan's broadcasting organisation NHK that the vessels bear a "striking resemblance" to those used by defectors from North Korea.
"(The boats) are made of wood and are old and heavy. They can't travel very fast and the engines are not powerful enough to turn the ships against the currents," he explained.
Mr John Nilsson-Wright, head of the Asia programme at the Chatham House policy institute, told CNN that defectors could be taking the more dangerous route across the Sea of Japan because traditional routes, such as crossing the border into China, are harder now that they are policed.
"What we do know is that for those people living outside of (North Korean capital) Pyongyang... life remains extraordinarily hard, and it may be an economic necessity as much as a desire for political freedom (that is) encouraging some people in the North to try and leave the country," Mr Wright said.
Mr Jun Okumura, a visiting scholar at the Meiji Institute for Global Affairs, agreed.
"I would say that defectors would be the most likely explanation, and the fact that there have been so many cases in such a short space of time is worrying because it suggests there is serious instability just below the surface in North Korea," he said.