A “private complaint” is behind the continued detention of a U.S. Navy veteran in Iran, the semi-official Mehr news agency reported Friday.

Michael R. White, 46, has been in detention since July. He is the first known American to be held in Iran since U.S. President Donald Trump took office. His family says he traveled to Iran to visit his girlfriend, who he met online, and was arbitrarily detained.

The Friday report quoted prosecutor Gholamali Sadeghi as saying the case is still “under investigation,” without elaborating. He did not confirm reports that the man faces security charges. Under Iranian law, a private complaint would refer to allegations made by a citizen, not the state.

Although the exact circumstances of White’s detention remain unclear, Iran in the past has used its detention of Westerners and dual nationals as leverage in negotiations.

At least three other American citizens are being held in Iran. Another U.S. man has been missing in Iran for over a decade.

White’s mother, Joanne White, previously confirmed to the New York Times her son, who lives in Imperial Beach, California, went to Iran to see his girlfriend and had booked a July 27 flight back home to San Diego via the United Arab Emirates.

She filed a missing person report with the State Department after he failed to present himself for the return journey. She added that he had been undergoing treatment for a neck tumor and has asthma.

Michael White worked as a cook for the Navy and left the service 10 years ago, according to a spokesman for the family, who insisted White was not a spy and had never been one. The spokesman, Jonathan Franks, said White had recently worked as a janitor.

The U.S. and Iran do not maintain diplomatic relations, and communications between the two nations are passed along by Swiss diplomats.

AP contributed to this report