TOKYO (Reuters) - Eight bodies, which had been reduced partly to skeletons, were found on Monday in a small wooden ship that washed up on a beach in the sea of Japan, the Japan Coast Guard (JCG) said.

The ship came ashore on a beach 70 km (44 miles) north of a marina where police last week found eight men who said they were from North Korea. Police said they appeared to be fishermen whose boat, found nearby, had run into trouble.

The JCG said they were working to establish the nationalities of the eight bodies on the ship.

The bodies of two males, similarly partly skeletonized, were also found at the weekend on the western shore of the Sea of Japan island of Sado.

Although the nationalities of these two have not yet been established, what appeared to be North Korean cigarettes and life jackets with Korean lettering on them were nearby, the JCG’s Sado station said.

Both local police and the JCG said the two may have been from North Korea.

The incidents come at a time of rising tension over North Korea’s nuclear arms and missile programs after President Donald Trump redesignated the isolated nation a state sponsor of terrorism, allowing the United States to levy further sanctions.

Experts say North Korea’s food shortages could be behind what is potentially a series of accidents involving North Korean ships.

“North Korea pushes so hard for its people to gather more fish so that they can make up their food shortages,” said Seo Yu-suk, research manager of North Korean Studies Institution in Seoul.

Small and old North Korean ships that sail beyond its coastal waters are vulnerable to bad weather, he said.

Yoshihiko Yamada, professor at Japan’s Tokai University, said fishermen operating in the Sea of Japan have just entered a season of hostile weather conditions.

“During the summer, the Sea of Japan is quite calm. But it starts to get choppy when November comes. It gets dangerous when northwesterly winds start to blow,” he said.

A total of 43 wooden ships that were believed to have come from the Korean peninsula washed up on Japanese shores or were seen to be drifting off Japan’s coast from January to Nov. 22 this year, compared with 66 ships for the whole of last year, the JCG said.