Washington/San Francisco: Facebook Inc. said it had data-sharing partnerships with four Chinese consumer-device makers, including Huawei Technologies Co., escalating concerns that the social network has consistently failed to tell users how their personal information flows beyond Facebook.

The disclosure came after Mark Warner, the top Democrat on the Senate Intelligence Committee, said earlier Tuesday that he saw “a serious danger" that Facebook shared user information with Chinese device makers. Facebook said it was careful about the partnerships, which were designed to help smartphone makers build custom versions of Facebook’s app. Still, the confirmation is likely to heighten scrutiny of the company’s privacy practices if the deals weren’t explicitly disclosed to users.

“Facebook’s integrations with Huawei, Lenovo, OPPO and TCL were controlled from the get go—and we approved the Facebook experiences these companies built," Francisco Varela, the company’s vice president of mobile partnerships, said in a statement. “Given the interest from Congress, we wanted to make clear that all the information from these integrations with Huawei was stored on the device, not on Huawei’s servers."

The New York Times reported on Sunday that the company had for years allowed deals with about 60 phone and device manufacturers, giving them access to vast amounts of information on users and their friends. It’s not clear yet whether any of the partners abused the data or transferred it to unauthorized parties.

If users weren’t aware of device makers’ access, the deals could violate a 2011 US Federal Trade Commission consent decree.

The confirmation that Chinese device makers, especially Huawei, were among the manufacturers with access to user data raised even more questions among US lawmakers about how the information was stored and used.

“The news that Facebook provided privileged access to Facebook’s API to Chinese device makers like Huawei and TCL raises legitimate concerns," senator Warner of Virginia said.

Some US lawmakers, many of whom were already critical of Facebook’s response to earlier inquiries into the Cambridge Analytica data scandal, have been sceptical of Facebook’s explanations of its latest data lapse, and demanded more accountability. Senators John Thune and Bill Nelson, the Republican chairman and top Democrat, respectively, on the Senate Commerce Committee asked chief executive Mark Zuckerberg in a letter for a full list of device makers with which Facebook had agreements. They also asked how the company verifies compliance with the agreements and whether Zuckerberg would like to amend his April testimony to the committee in which he said that users have “complete control" over how their data is shared.