WASHINGTON >> Before his arrest in Russia, U.S. soldier Gordon Black not only broke Army rules by traveling to the Russian city of Vladivostok without authorization, but he did so after passing through China, the Pentagon said today.

Details about Black started to emerge today of risk-taking behavior that saw the 34-year-old Army staff sergeant’s luck run out after he followed his girlfriend to Russia while he was on personal leave from military service.

Russia has charged him on suspicion of theft. His mother says she thinks he was set up by his Russian girlfriend.

The case presents yet another diplomatic headache for the United States, which has warned U.S. citizens against travel to Russia and has been wrestling with other high-profile detentions there.

That includes a drugs case against basketball star Brittney Griner, who was freed last year in a prisoner swap, and Wall Street Journal reporter Evan Gershkovich, who has been detained on espionage charges, which he and his employer deny.

Black enlisted in the Army as an infantryman in 2008 and had been assigned to Camp Humphreys in South Korea. He was set to return to Fort Cavazos in Texas, the U.S. Army said in a statement.

“Instead of returning to the continental United States, Black flew from Incheon, Republic of Korea through China to Vladivostok, Russia, for personal reasons,” the Army added.

The Army said there was no evidence that Black planned to stay in Russia after his personal leave ended.

Black’s mother, Melody Jones, told ABC News that she had a conversation with her son before he left and told him that she was uncomfortable with him going to Russia, but he went anyway.

“I knew something was going to happen. I felt like he was being set up by her,” Jones said.

Black’s case is the latest headache for the U.S. Army, after U.S. Army Private Travis King was held in North Korea for over two months after his surprise dash across the heavily militarized border dividing the Korean peninsula. King is now back in the United States.

The Army said the Russian Interior ministry informed the U.S. embassy in Moscow on May 3 that Black had been arrested in Vladivostok the day earlier for “theft of personal property.”

Black, who has deployed to both Iraq and Afghanistan, is currently in a pre-trail detention facility, the Army said.

“He will remain in detention until his next hearing pending determination,” it added.

The Russian interior ministry in Vladivostok said a 32-year-old woman had filed a complaint against Black.

The two had met in South Korea, the ministry said. The American had come to Vladivostok to visit her, the two had an argument, and she later filed a police report accusing him of stealing money, it said. He was arrested in a hotel, having bought a plane ticket to return home.

The Russian Foreign Ministry said the case had no political element and there were no allegations of espionage.

Separately, Moscow’s court service said today that a court had remanded a U.S. citizen whom it named as William Russell Nycum in custody for 10 days for “petty hooliganism.”