“Every single Uighur person can tell you they’ve lost someone, but when it’s your wife and she was waiting to leave China, it’s especially hard,” said Mr. Nizamidin, 28, now a building contractor in Adelaide. They were high school sweethearts, and she was learning English to migrate to Australia when arrested, he said.

“I’m very worried about her, because there’s been no information,” Mr. Nizamidin said. “Everyone is talking about the camps, even at the U.N., but the prisons are taking in more and more, and they’re under even stricter control.”

The expanding population in prisons raises questions about Xinjiang officials’ recent avowals that most of the inmates in re-education camps — a separate system of incarceration — have been released.

Uighur activists and overseas Uighurs with relatives in the camps have disputed Beijing’s claim that the camps are shrinking. Interviews and government documents indicate that former camp inmates may be pressed into assigned labor or other kinds of detention.

And Uighurs living abroad who spoke with The Times said a sizable fraction of people held in re-education camps end up in prisons, citing messages from relatives still in Xinjiang. Detainees, they said, have been arrested and convicted after interrogators in the camps decided that they had committed offenses and sent them for criminal investigation.

“If you’re willing to play along, and you work hard to show your loyalty to the Communist Party, then maybe you can move into less coercive detention,” said James Leibold, an associate professor at La Trobe University in Australia who has studied the security offensive in Xinjiang. “But if you show any signs of resistance, it’s escalated to formal imprisonment.”

Security in Xinjiang has been tight for years. In 2009, hundreds were killed during ethnic riots in the regional capital, Urumqi, prompting the government to start instituting harsher policies.