Ukrainian and U.S. government officials reportedly said North Korean troops have not been seen at the front lines of the Russia-Ukraine war for roughly two weeks.

The New York Times quoted the officials as saying on the condition of anonymity on Thursday that the deployed North Korean forces have been pulled off the front lines after suffering heavy casualties.

The report quoted the American officials as saying the decision to pull the North Korean troops off the front lines may not be a permanent one.

The officials reportedly said one possibility is that the North Korean troops could return after getting further training or after Moscow devises new ways of deploying them to avoid heavy casualties.

According to Gen. Oleksandr Syrsky, Ukraine’s top military commander, the number of North Korean forces is only half what it was when they arrived in Russia in November, when it stood at 11-thousand.