A Russian politician who disappeared from public view after criticizing Vladimir Putin’s illegal invasion of Ukraine has reportedly turned up at the U.S.-Mexico border. Viktor Kamenshchikov, who is in his early thirties, quit the the Communist Party after speaking out against the Feb. 24 invasion and then stopped appearing at meetings of the Duma, or city council, in the Far Eastern port city of Vladivostok. Citing law enforcement sources, Russian news agencies reported Thursday that he had been held at the U.S. southern border. “They detained him. What for is not yet clear, presumably for illegal border crossing,” one source told the RIA-Novosti agency. Kamenshchikov reportedly has a child with U.S. citizenship by birthright. There has been no confirmation of his detention from American officials.