Sam Brownback, ambassador-at-large for International Religious Freedom, told a State Department press conference on Thursday he has received reports of U.S. citizens and legal residents imprisoned in China’s re-education camps for Muslims in Xinjiang province.

Brownback, who recently returned from a trip to Asia, spoke out against China’s “increasing aggression towards people of faith.”

“China is at war with faith, but it is a war they will not win,” he said.

Brownback called out Chinese acts of oppression against Muslims, Tibetan Buddhists, and Christians, placing particular emphasis on the “horrific conditions and abuses” in the Xinjiang internment camps where a million Muslims have been held. A number of the prisoners have reportedly died in captivity at what China outrageously describes as “boarding schools” or “vocational training camps.”

Brownback said he received new information about a man with American legal status held in the Xinjiang camps right before the press conference began.

“Just as I walked over here, I received another email from a gentleman in the United States whose father is still in Xinjiang who hasn’t – he’s not been able to reach him for months, 75-year-old man, doesn’t know whether – where he is and whether he’s still alive,” Brownback said.

“If I get verified, this gentleman that I just was reading the email about has legal status in the United States. Now, he’s not a U.S. citizen, but he had legal status being here, traveled back to Xinjiang after being here with his son in California, and then has not been heard from since,” he clarified later in the press conference.

Brownback said the State Department has also received reports about Kazakh, Kyrgyz, and Turkish nationals held in the camps. Most of the Muslims in Xinjiang belong to the Uighur minority, a Turkic ethnic group. Turkey is the only major Islamic power to object to China’s harsh treatment of its Muslim population.

The Trump administration has unquestionably been the most vocal and active defender of Xinjiang’s Muslims. Brownback said on Thursday that the possibility of level sanctions against Chinese officials under the Global Magnitsky Act is still on the table. Sanctioned individuals could include the top Communist Party official in Xinjiang, who played a leading role in the oppression of Tibet before he was put in charge of the Uighur situation.

China would react with fury to any such sanctions, especially if a high official of the Communist Party is targeted. The Chinese government dismisses all action on behalf of Xinjiang’s Muslims as unacceptable interference in its internal affairs.

“Global Magnitsky is handled by Treasury Department, and when people are ready to make announcements, they will,” he said.

The ambassador noted that Chinese officials have not responded to numerous requests by family members in other countries seeking information about missing relatives in Xinjiang. He described a frustrating encounter with Chinese representatives at the United Nations earlier in March:

They claimed at that time – and the story has been morphing over time of what is taking place in Xinjiang – at first they denied anything was happening, nothing’s going on here. And then later they said they were vocational training camps, and that’s what the individual was saying at this time, that these continue to be vocational training camps. To which I said, “I get and have lists of names, hundreds of names that are sent to me that people that can’t find their relatives. Would you please help me find them and tell their relatives where they are?” To which there was no response from the Chinese official.

CNN cited multiple State Department sources on Friday who said they are aware of multiple persons with American legal status held in the Xinjiang camps. One source said the number of such individuals is not large but could provide no additional details due to privacy concerns.

The State Department explained on Thursday that because China “does not recognize dual nationality,” it can be difficult to provide consular services to people with U.S. legal status in China, and they could be “subject to additional scrutiny and harassment.”

Brownback referenced a meeting Secretary of State Mike Pompeo held on Wednesday with a survivor of the Xinjiang camps and the relatives of people who are still incarcerated there. The Uighur survivor, Mihrigul Tursun, said she was separated from her children, held in an overcrowded cell, and tortured with beatings and electrocution. Other Muslim veterans of the camps said China confiscated their Qurans and forced them to violate Islamic dietary laws in an effort to “deprogram” them away from their religion.

“We’re working to convince the Chinese that this practice is abhorrent and ought to be stopped,” Pompeo said on Wednesday.

“China must release all those arbitrarily detained and end its repression,” Pompeo said online after his meeting with the Uighurs. “The world cannot afford China’s shameful hypocrisy toward Muslims. On one hand, China abuses more than a million Muslims at home, but on the other, it protects violent Islamic terrorist groups from sanctions at the U.N.”

The latter comment was a reference to China’s repeated protection of Jaish-e-Mohammad terrorist leader Masood Azhar against sanctions. Jaish-e-Mohammad is the Pakistan-based extremist organization that claimed responsibility for a major attack on Indian troops in the disputed Kashmir province in late February, an incident that brought India and Pakistan to the brink of war.