North Korea's security authorities have dispatched dozens of workers to coal mines in China's northeastern province of Jilin through illicit methods since the middle of May, a U.S.-based media report said Wednesday.

Citing a source from the North's Ryanggang Province, Radio Free Asia reported that officials of the North's State Security Department stationed in the North Korean province sent 30 North Korean workers on July 2 to Changbai County in Jilin, an area bordering North Korea's Pochon County across the Tumen River. The workers were sent over very late at night, which may indicate that they did not have the proper documents.

Another source said the security officials in Ryanggang dispatched North Korean coal mining laborers in two or three separate instances over the past two months through unauthorized crossing of the Tumen River, the RFA claimed.

The North Korean workers are paid 41,000 won ($36) per month in return for mining coal there, according to the source.

The source also said the North Korean workers are not punished at all; they are simply caught by the Chinese security authorities and repatriated to the North.  (Yonhap)