The U.S. ambassador to Japan questioned in a social media post on Friday whether China’s Defence Minister Li Shangfu had been placed under house arrest, adding to confusion about the state councillor’s more than two week absence from public view, according to Reuters.

In a post on X, formerly Twitter, Rahm Emanuel wrote: “1st: Defense Minister Li Shangfu hasn’t been seen or heard from in 3 weeks. 2nd: He was a no-show for his trip to Vietnam. Now: He’s absent from his scheduled meeting with the Singaporean Chief of Navy because he was placed on house arrest???”

China’s foreign and defence ministries did not immediately respond to requests for comment. The U.S. embassy in Tokyo said it did not immediately have further comment.

Li, 65, abruptly pulled out of a meeting with Vietnamese defence leaders last week, Reuters exclusively reported on Thursday. He was last seen in Beijing on Aug. 29 delivering a key-note address at a security forum with African nations.

The U.S government believes Li has been placed under investigation, the Financial Times reported on Friday, citing three U.S. officials and two people briefed on the intelligence. The report did not state the nature of the investigation.

Li’s absence follows China’s unexplained replacement of its foreign minister, Qin Gang, in July after a prolonged period out of public view and a shake-up of the leadership of the People’s Liberation Army’s elite Rocket Force in recent months.

Like Li, Qin is one of China’s five state councillors, a cabinet position that ranks higher than a regular minister.

These moves have raised questions from analysts and diplomats about a lack of transparency in China’s leadership at a time when its economy is slowing and its relations with rival superpower the United States have soured over a range of issues.

Before Li was appointed to his post in March, he had headed the military’s procurement unit.

In a rare notice in July, the unit said it was looking to “clean-up” its bidding process and invited the public to report irregularities dating back to 2017. There has been no update on possible findings.

Li’s absence is being particularly closely watched by the U.S., which has refused to drop sanctions imposed on him in 2018 for buying weapons from Russia’s largest arms exporter, Rosoboronexport.

Chinese officials have repeatedly said they want those sanctions dropped to facilitate better discussions between the two sides’ militaries. U.S. Defence Secretary Lloyd Austin attempted talks with Li during a defence conference in Singapore in June, but did not get beyond a handshake.

Wen-Ti Sung, political scientist at the Australian National University, said while Li had been a “roadblock” in U.S.-China military relations his unexplained absence is problematic for China’s international relations in other ways.

“Other countries will be wondering something as basic as whose number to call when they want to set up military dialogues with China,” he said.