A U.S. Army sergeant stationed in Korea has been detained in Russia, accused of stealing from a woman, two Pentagon officials said Monday.

Staff Sgt. Gordon D. Black was arrested on May 2 in Vladivostok. It is unclear how he got there but he was in the process of changing duty stations from Korea to Fort Cavazos (Ft. Hood) in the U.S. He was not there on official travel.

The soldier’s mother, Melody Jones, said he was in Russia visiting his girlfriend.

“Please do not torture him [or] hurt him,” Melody Jones said when asked about her message to the Russians.

National Security Council spokesman John Kirby told reporters that the U.S. is “aware of this case and other matters related to Russia,” but he said he couldn’t “say much about it right now.” NBC News first reported that a soldier had been detained in Russia over the weekend.