(CNN) A bipartisan group of US lawmakers said the Trump administration's response to China's alleged abuses of the largest Muslim Uyghur ethnic minority in Xinjiang was inadequate and urged it to hold Beijing to account.
"The administration has taken no meaningful action in response to the situation in (Xinjiang)," lawmakers wrote in a letter to Secretary of State Mike Pompeo, four months after they originally called on him to take action on this issue.
CNN has reached out to the State Department for comment.
As many as two million Uyghurs are estimated to have been imprisoned in huge detention centers in China's far west, according to a US government report.
The human rights crisis in Xinjiang has drawn increasingly harsh criticism from across the world. At a UN hearing in November, more than a dozen countries called on Beijing to end its "arbitrary detention" of Uyghurs.
A former detainee told CNN she witnessed abuse and torture, and lost one of her sons during her time in the camps.
Beijing has repeatedly denied it is detaining Uyghurs against their will, calling the camps "vocational training centers" and suggesting they are providing education.
In their letter Monday, the US lawmakers, led by House Committee on Foreign Affairs Chairman Eliot Engel, said that "over a million Uyghurs and other Muslim ethnic minorities have been interned in 'political re-education camps' without due process as part of a broader attempt to wipe out their separate identity, language, and history."
"Global responses to these abuses have been insufficient. Of particular concern are reports of US companies that may be contributing to Beijing's persecution of Uyghurs through their support or commercial ties to Hikvision and Dahua -- two Chinese tech giants that have profited from the surge of security spending in Xinjiang," the letter added.
It also pointed to plans by Frontier Services Group, a Hong Kong-based company that counts former Blackwater CEO Erik Prince among its investors, to build a "training center" in Xinjiang.
"These examples demonstrate not just the need to increase public awareness of human rights issues in (Xinjiang), but also impose consequences on PRC officials responsible and those who enable their abuses," the letter said. "Rhetoric without action will only embolden Beijing."
Lawmakers requested information on whether the US monitors the use of American technology in facilitating the surveillance and detention of Muslim minorities in Xinjiang, and details of "any US companies that are allegedly providing technology transfers, sales, or security training for Chinese government officials or closely associated entities that operate in the Xinjiang Uyghur Autonomous Region."
They also called on the Trump administration to reveal its plans, either unilaterally or with allies, for "holding Beijing accountable."
The letter comes as Beijing is facing a growing global backlash over the situation in Xinjiang, as reports of alleged abuses their stack up. Last month, Turkey -- which has a large Uyghur population -- said the detention camps were a "great shame for humanity."
In a strongly-worded statement, Foreign Ministry spokesman Hami Aksoy said hundreds of thousands of prisoners were subject to "torture and political brainwashing" in China's camps, and called on the UN and the international community "to take effective measures in order to bring to an end this human tragedy in Xinjiang."
Lawmakers in Indonesia and Malaysia have also expressed alarm over the alleged abuses in Xinjiang, and called for a full accounting of the "re-education camp" system.