Facebook isn't the only company in the hot seat for its relationship with Chinese tech firms. On Thursday, Alphabet, Google's parent, came under scrutiny for having ties with those firms, too.

In an open letter to Alphabet CEO Larry Page, Sen. Mark Warner expressed concern about the company's dealings with Huawei and Xiaomi, two big Chinese device makers. The Virginia Democrat also raised concerns about Alphabet's relationship with Tencent, a Chinese platform company.

The possibility of the Chinese firm having access to data from Google "raises national security concerns," Warner said in his letter. Warner also pushed Page to disclose more information about Google's deals with those companies.

In recent weeks, Huawei has been called out for allegedly having ties to the government in Beijing. 

A Google spokeswoman said the company looks forward to addressing Warner's concerns. "Like many US companies, we have agreements with dozens of OEMs around the world, including Huawei," the spokeswoman said. "We do not provide special access to Google user data as part of these agreements, and our agreements include privacy and security protections for user data."

Huawei, Xiaomi and Tencent didn't respond to requests for comment.

Warner's letter comes a little less than a week after The New York Times reported that Facebook had data-sharing partnerships with more than 60 device makers, including Apple and Samsung. The social network later acknowledged Huawei and other Chinese manufacturers were included in those partnerships.

Republicans also appear to be concerned by Google's relationship with Huawei. Sen. Tom Cotton of Arkansas and Rep. Mike Conaway of Texas are reportedly looking into the ties between the companies. 

Cotton's and Conaway's offices didn't immediately return requests for comment.

The alarm from Congress underscores tensions between the US and China over concerns that Beijing could digitally spy on Americans.

Google and Facebook have been under intense scrutiny over their data-collection practices. Facebook has been rocked by a scandal involving Cambridge Analytica, a digital consultancy with ties to the Trump presidential campaign, that improperly accessed personal information on up to 87 million Facebook users.

The scandal eventually landed Facebook CEO Mark Zuckerberg on Capitol Hill for 10 hours of congressional testimony about everything from Facebook's data-hungry advertising business to the role of social network in the 2016 US election.

After the hearings, members of Congress said they'd ramp up their scrutiny of Google and Twitter. 

"A lot of the concerns raised in the hearings this week were around privacy," Warner told CNET after the Zuckerberg hearings. "Obviously that is a huge issue and one that not only Facebook needs to address, but Twitter needs to address, in a sense Google and YouTube as a single entity need to address."

Last November, all three companies testified before Congress regarding the integrity of their platforms. But none of them sent their CEOs. Instead, they tasked their top lawyers with enduring the public scolding. The decision didn't sit well with lawmakers who wanted answers from the top of the companies rather than their polished lawyers.

Update, 4:15 p.m. PT: Adds comment from Google. 

Cambridge Analytica: Everything you need to know about Facebook's data mining scandal.

iHate: CNET looks at how intolerance is taking over the internet.