North Korean boat sinks after colliding with Japanese patrol vessel in the Yamatotai area, northwest of Noto Peninsula.

Japanese authorities said they rescued all of about 60 North Korean fishermen whose boat collided with a Japanese patrol vessel and sank Monday in an area crowded with poachers.

Coastguard officials earlier said that only about 20 North Korean crew members were thrown into the sea after their steel boat collided with a Japanese Fisheries Agency inspection boat in Japan’s exclusive economic zone off the country’s northern coast.

Officials later said they rescued far more than first thought. No one was missing.

The North Korean boat sank about half an hour after the collision in the Yamatotai area, known as rich grounds for squid fishing northwest of the Noto Peninsula.

The North Korean boat had made an unauthorised entry into Japan’s exclusive economic zone and the collision occurred just as the Japanese patrol boat was warning it to move out, Fisheries Agency official Satoshi Kuwahara told reporters. He said officials were investigating whether the North Korean ship was actually conducting illegal fishing, and how the two ships collided.

Agricultural, Forestry and Fisheries Minister Taku Eto said the North Korean boat suddenly changed course before crashing into the Japanese ship and sinking, the Kyodo news agency reported.

The coastguard’s regional office in Niigata said officials handed the fishermen to another North Korean boat in the area after notifying The North’s rescue coordination centre to arrange their way home. It said the North Korean crew members had no life-threatening conditions.

Fisheries Agency officials said the Japanese patrol ship had no major damage and was able to move on its own.

Japan and North Korea have no diplomatic ties.

The two countries also have disputes over Japan’s 1910-1945 colonial rule of the Korean Peninsula, as well as North Korea’s nuclear and missile development and the North’s abduction of Japanese citizens in the 1970s and 1980s.

During Monday’s parliamentary session, Prime Minister Shinzo Abe pledged to thoroughly investigate Monday’s incident.

“We will resolutely respond to prevent poaching by foreign fishing boats in the Japanese exclusive economic zone,” he said.

Japan has stepped up patrols in the area in recent years as North Korean squid poaching has surged. This year, ships from Japan’s Fisheries Agency and coastguard have been patrolling in the area since May, Kuwahara said.

Experts say the increase in North Korean squid poaching is due to the country’s campaign to boost fish harvests. With Russia also stepping up its patrols against poaching, desperate North Korean fishermen under pressure to meet their quota have opted to head to Japanese economic waters, increasing the risk of clashes with Japanese patrol boats, Satoru Miyamoto, a Seigakuin University professor and expert on North Korean politics, diplomacy and military issues, told Japan’s NHK public television.

Japanese fisheries patrols have issued nearly 500 expulsion orders to poachers between May and August this year, most of them from North Korea, according to the Fisheries Agency. It said Japan last year made 5,315 such orders to foreign fishing boats in the area, many of them North Korean. Poachers also come from China, Russia and South Korea.

In June, Japan’s coastguard pushed more than 300 North Korean boats back in the same waters where Monday’s incident occurred. Japan also said an armed North Korean fishing boat aimed a gun at and threatened a Japanese patrol ship in August.

The North Korean poachers are believed to be related to an influx of “ghost boats” that have washed onto Japan’s northern coast, fisheries officials have said.