KORLA, China (AP) — Nobody knows what happened to the Uighur student after he returned to China from Egypt and was taken away by police. Not his neighbors, not his classmates, not his mother.

"Is he dead or alive?" the mother said, tears streaming down her face when Associated Press reporters visited her at home unexpectedly and showed her a photo of the student.

The student's friends think he joined thousands — possibly tens of thousands — of people who have been spirited away without trial into new indoctrination centers. The mass disappearances, beginning the past year, are part of efforts by Chinese authorities to use detentions and data-driven surveillance to impose a police state over the region of Xinjiang and its 10 million Uighurs, a Turkic-speaking Muslim minority that China says has been influenced by Islamic extremism.

Unprecedented levels of police blanket Xinjiang's streets in many cities. Cutting-edge surveillance systems track where Uighurs go, what they read, who they talk to and what they say.

Through rare interviews with Uighurs who recently left China, a review of government procurement contracts and unreported documents, and a trip through southern Xinjiang, the AP pieced together a picture of a campaign that's ostensibly rooting out terror — but instead instilling fear.

Most of the more than a dozen Uighurs interviewed for this story spoke on condition of anonymity for fear that Chinese authorities would punish them or their family members. The AP is withholding the student's name and other personal information to protect people who fear government retribution.

The Xinjiang regional government did not respond to repeated requests for comment. But China's government describes its Xinjiang security policy as a "strike hard" campaign that's necessary following a series of attacks in 2013 and 2014, including a mass knifing in a train station that killed 33. A Hotan city propaganda official, Bao Changhui, told the AP: "If we don't do this, it will be like several years ago — hundreds will die."

China also points to decades of heavy economic investment and cultural assimilation programs and measures like preferential college admissions for Uighurs.

Authorities refer to the detention program as "vocational training," but its main purpose appears to be indoctrination. Training sessions on "Mandarin, law, ethnic unity, de-radicalization, patriotism" are described as lasting anywhere from 3 months to 2 years.

In Korla, one center the AP visited was labeled a jail. Another was downtown on a street sealed off by rifle-toting police.

Southern Xinjiang, where Korla is located, is one of the most heavily policed places on earth.

In Hotan, police depots with flashing lights and foot patrols are set up every 500 meters. Motorcades of more than 40 armored vehicles rumble down city boulevards. Police checkpoints on every other block stop cars to check identification and smartphones for religious content.

Xinjiang's published budget data shows public security spending this year is on track to increase 50 percent from 2016 to roughly 45 billion yuan ($6.8 billion) after rising 40 percent a year ago. It's quadrupled since 2009, when a Uighur riot broke out in Urumqi, killing nearly 200 people.

But much of the policing goes unseen.

Shoppers entering the Hotan bazaar must pass through metal detectors and place their national identification cards on a reader while having their faces scanned. AP reporters were stopped outside a hotel by a police officer who said the public security bureau had been remotely tracking the reporters' movements by watching surveillance camera footage.

The government's tracking efforts have extended to vehicles, genes and even voices. A biometric data collection program appears to have been formalized last year under "Document No. 44," a regional public security directive to "comprehensively collect three-dimensional portraits, voiceprints, DNA and fingerprints." The document's full text remains secret, but the AP found at least three contracts referring to the 2016 directive in recent purchase orders for equipment such as microphones and voice analyzers.

China has also turned to a familiar low-tech surveillance tactic: recruiting the masses.

A Uighur businessman from Kashgar who fled China said his four brothers and his father were in prison because of his escape and that families tasked with spying on one another in his community had also been punished. Members from each were sent to re-education centers for three months, he told the AP.

A document obtained by U.S.-based activists and seen by the AP shows Uighur residents in the Hebei Road West neighborhood in Urumqi, the regional capital, being graded on a 100-point scale. Those of Uighur ethnicity are automatically docked 10 points. Being aged between 15 and 55, praying daily, or having a religious education, all result in 10 point deductions. A neighborhood police official in Urumqi surnamed Tao confirmed that every community committee in the city needed to conduct similar assessments.

Uighurs abroad say it's too risky to stay in touch with their families in China.

When Salih Hudayar, an American Uighur graduate student, last called his 70-something grandfather this summer, the elderly man told him kindly not to call again. He later heard his grandfather had been sent to an indoctrination camp.

A Uighur student who moved to Washington following the crackdown this summer said that after his move, his wife, a government worker still in Urumqi, messaged to say the police would show up at her home in 20 minutes. She had to say goodbye: after that she would delete him permanently from her contacts list.

Later, he couldn't help himself placing one last call home. His daughter picked up.

"Mom is sick but she doesn't want me to speak to you. Goodbye," she said.