Paul Whelan, a former U.S. Marine who was accused of spying in Russia, suggested in letters to his family that he was arrested in Moscow as “retaliation” for U.S. sanctions. According to the letters, which were obtained by Foreign Policy, Whelan wrote in March that his detention was “100% work related.” “Ask BW for support. Sanction retaliation,” he wrote in one letter, which was transcribed by his lawyer’s translator. Whelan worked as the global security director of BorgWarner, a Michigan-based auto-parts company—although the company told the magazine Whelan did not travel to Russia on a work-related trip. In another letter—this time written in his own handwriting—Whelan stated that he didn’t think Russians were detaining him to retaliate against BorgWarner specifically, but were looking to lash out against any U.S. company.

David Whelan, Whelan’s twin brother, told the magazine they haven’t been in contact with BorgWarner. Whelan was detained in Russia late last year over spying allegations, but Russian authorities have yet to produce any evidence supporting their claims.