Chinese intelligence officers began tracking an employee of the U.S. Commerce Department this spring, when he was in southwest China and where he has family members, at one point interrogating him about his prior service in the U.S. military, according to a U.S. government document.

The man, who is an American citizen, has been prevented from leaving China since mid-April, according to the document, a State Department cable that was obtained by The New York Times.

The cable, from the U.S. Embassy in Beijing, was dated May 2 and sent to officials in Washington, including Secretary of State Marco Rubio and White House aides on the National Security Council.

On April 14, the Chinese officers seized the man’s passport, credit card, cellphone and iPad while he was in Chengdu, the capital of Sichuan Province, the cable said. The officers, who worked for the Ministry of State Security, China’s main intelligence and counterintelligence agency, returned the passport on April 22 but told the American he could not leave the country. His wife is in the United States.

The cable gives a glimpse into the operations of the secretive Ministry of State Security as it increased pressure on the American during his stay in China. It also lays out efforts by U.S. diplomats to get him to Beijing from Chengdu in early May, while Chinese officers continued to conduct surveillance on him.

The man’s situation became public over the weekend, after American news organizations reported on his plight. The cable obtained by The Times did not identify the man by name or give details about his background, but it offers new information about his situation.