An American detained in Iran in July 2018 is being investigated on possible security charges, an Iranian prosecutor was quoted as saying on Friday, in a case that could further strain turbulent relations between Iran and the United States. Several Americans have been detained in Iran in recent years, mostly on security-related charges including espionage, Reuters reported. Gholamali Sadeqi, prosecutor in the northeastern city of Mashhad, said authorities were investigating security-related accusations against Michael White, according to the official news agency Mehr. Sadeqi also said White, a 46-year-old US Navy veteran, had been arrested because of a “private complaint” filed against him. In the past, “private complaints” filed by the Revolutionary Guards or other security bodies have led to arrests of activists and closure of newspapers. Iran confirmed White’s arrest earlier this month after the New York Times reported that White was arrested in July while visiting his Iranian girlfriend. London-based news website IranWire has reported that White was being poorly treated in prison, but Tehran has denied this, according to Reuters.