South Korea says the 31 North Koreans who crossed the inter-Korean maritime border in the Yellow Sea on Saturday have expressed no intentions to defect to South Korea.

A government official in Seoul said that because there were no children on the boat, it is highly likely that the vessel drifted southward by accident.

The official said Seoul will treat this case in line with its principle of respecting North Koreans’ wishes on whether they want to remain in the South or want to return to the North.

The 31 North Koreans, 20 of whom are female, crossed the Northern Limit Line in waters northeast of the border island of Yeonpyeong at 11 a.m. on Saturday on a five-ton wooden fishing vessel.

South Korean authorities expect that completing the investigation into the matter will take time due to the relatively large number of North Koreans who were on the boat.