An American soldier currently detained in Russia has allegedly admitted his guilt over accusations of stealing from his girlfriend, state media reported Thursday.

U.S. Staff Sergeant Gordon Black was placed in pre-trial detention after he was detained at a hotel in the city of Vladivostok on May 2. The Pentagon says Black, who was posted to South Korea, made his ill-fated trip to Russia without the authorization of the U.S. Army.

He is now “cooperating” with the investigation after “he admitted” guilt, a representative of the local interior ministry told RIA Novosti. The press service of the Ministry of Internal Affairs for the Primorsky Territory separately told the Interfax news agency that Black had confessed and the “investigation into the criminal case continues.”

Authorities in Russia say they received a complaint from a 32-year-old woman in Vladivostok alleging that her romantic partner, a foreign citizen that she’d met while working in South Korea, had stolen money from her. Police later found Black at a hotel and arrested him on theft charges as he was preparing to fly home, according to TASS.

Black has been charged with “theft causing significant damage,” meaning he could face a sentence of up to five years in prison if convicted.