A U.S. Navy veteran jailed in Iran since July is being held on a “private complaint,” an Iranian news agency reported Friday.

Michael White, 46, was detained after he traveled to Iran to visit his girlfriend, who he met online, his family said.

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He’s the first known American to be detained in Iran since Donald Trump became president.

According to the Mehr News Agency, prosecutor Gholamali Sadeghi said the case against White is still “under investigation” though he did not go into details nor did he confirm whether White is facing security charges. Under Iranian law, a private complaint refers to allegations made by a citizen, not the state.

Sadeghi's explanation of White's detention came a day after the U.S. freed Marzieh Hashemi, an American-born journalist who has worked for decades for Iranian state TV. She was released from U.S. custody after testifying before a grand jury in Washington.

Meanwhile, the push to release White continues.

His mother, Joanne White, said her son was scheduled to return to the U.S. from Iran through Dubai on July 27, but that her son never boarded the flight.

She filed a missing-person report with the State Department, prompting the Department of Homeland Security to contact her. The State Department told her three weeks ago that he’s currently in an Iranian prison, the report said.

“All I know is that he is alive and they were putting in a request for a consular visit by the Swiss,” she told the newspaper. The Swiss Embassy in Iran represents the U.S. The formal U.S.-Iranian diplomatic relations ceased about 40 years ago following the hostage crisis.

A State Department official told Fox News that they are aware of the reports of U.S. citizens in Iranian detention.

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According to the Times, there are at least three other Americans currently being detained in Iran. Two of them are of Iranian descent while the other American citizens have been missing in Iran for over a decade.

White’s mother said her son visited the country “five or six times” to meet his girlfriend. She said she does not know the charges he's facing. She noted that her son has undergone chemotherapy and radiation treatment for a neck tumor and is suffering from asthma.

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Fox News' Lukas Mikelionis and Greg Norman contributed to this report.