A Russian computer programmer has been arrested in Spain under a U.S. warrant, though authorities remain tight-lipped about the reasons for his arrest. The Russian embassy in Madrid confirmed the arrest of Pyotr Levashov on Sunday but declined to give further details, saying only that the embassy was notified Friday. Spanish authorities have also not commented on the matter. But Russia’s state-run RT news network reported that Levashov was arrested for suspected involvement in the hacking attacks carried out during the U.S. presidential election in 2016. U.S. authorities have accused Russia of using hackers to meddle in the election on behalf of now-President Trump, a claim that has been denied by the Kremlin. A U.S. Justice Department official was cited by Reuters as saying Levashov’s arrest was a matter of a criminal investigation, and not one concerning national security. The arrest comes after Spanish police arrested another Russian programmer in January in what was described as a financial fraud case.