North Korea is urging the U.S. to play a role in the repatriation of 31 North Koreans whose boat crossed into South Korean waters last month.

Pyongyang Broadcasting Station, which is a North Korean radio station that airs propaganda against South Korea, says the North Korean chief delegate to U.S.-North Korea colonel-level talks sent a protest letter to the U.S. military on Sunday urging for U.S. intervention in the return of the North Koreans.

The broadcaster also said that the probe conducted by the U.N. Command and South Korea into the North Koreans’ entry into South Korea had no scientific backing and that the results were fabricated.

The U.N. Command and the Seoul government say they have confirmed that four of the 31 North Koreans wish to defect to South Korea. Both of them say that this has been conveyed to North Korea.