Japan put its coastal security forces on alert on Tuesday after a wooden boat with eight decomposed bodies of men washed up on the shore in Akita Prefecture in the northern part of the country, reported The Washington Post. Their identities have not yet been determined.

The boat had washed up on the shore on Monday. “The coast guard and the police have to cooperate to step up sea patrols around Japan,” the chief government spokesperson Yoshihide Suga said. “The government intends to improve this to ensure we can guard against suspicious boats or people arriving in Japan.”

This is the latest of a number of similar incidents in recent times, BBC reported. On November 24, a wooden boat carrying eight men – alive and in good health – washed up at the city of Yurihonjo in the same region. The men had identified themselves as North Korean fishermen who entered Japanese waters by mistake while looking to catch squid.

Two bodies were found over the weekend at Sado island, Reuters reported. The Japanese Coast Guard said they had found a pack of North Korean cigarettes and other belongings in Korean language.

Experts said that food shortage in North Korea could be the reason why the bodies of so many fishermen were being found. “North Korea pushes so hard for its people to gather more fish so that they can make up their food shortages,” Seo Yu-suk, research manager of North Korean Studies Institution in Seoul, South Korea, was quoted as saying by Reuters.