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Google is firing back at the U.S. Department of Labor's allegations of gender discrimination at the company by highlighting its own "scientific and robust" analysis for ensuring pay equity.

In a blog post published on Tuesday, Eileen Naughton, vice president of people operations at Google, wrote the company was "quite surprised" at the allegations levied against Google last week.

"We were taken aback by this assertion, which came without any supporting data or methodology," she said.

People stand under a sign at Google headquarters in Mountain View, California, on Jan. 5, 2010. Robert Galbraith / AFP - Getty Images Pool, file

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The U.S. Department of Labor last week alleged the search giant had "systematic compensation disparities against women." The allegations stem from a January lawsuit in which the Department of Labor asked Google to hand over compensation data.

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Although the tech giant has held off from submitting records that would include private or identifying information about its employees, Naughton said Google has already responded to 18 separate requests, producing hundreds of thousands of documents.

"Every year, we do a comprehensive and robust analysis of pay across genders and we have found no gender pay gap. Other than making an unfounded statement, which we heard for the first time in court, the DoL hasn’t provided any data, nor shared its methodology,” Google told NBC News.

Google made its methodology for determining equal pay available to other companies last year. Naughton said it is so scientific that Google has also been able to expand the analysis to include race in the United States.

The company uses four steps to ensure pay equity. First, men and women are compared by the job level and its family (for instance, a level 4 account manager working in Mountain View.)

Suggested and adjusted compensation is then compared. Then, the data is held constant to account for metrics such as performance ratings. Google says it then assesses whether there's a difference, and if there is, will make an adjustment to bring parity, with all of those factors considered.

"I think it is really interesting because the methodology they're putting out, if accurate, would be a great way to do things," Frida Polli, founder of neuroscience start-up Pymetrics and an equal pay advocate, told NBC News. "I'm confused why they would have this methodology and find themselves in this situation."

On Equal Pay Day earlier this month, Google tweeted it was "proud" to have closed the gender pay gap globally.

Let’s make every day #EqualPayDay. All employers can take steps to eliminate the gender and race pay gaps, today → https://t.co/KTuGTJMV16 pic.twitter.com/rBciSK21uF — Google (@Google) April 4, 2017

Polli said she sees a "disconnect" in the case and that the allegations have led to more questions than answers. For now, the Department of Labor is declining to comment.

Google has experienced allegations of bias in the past, when in 2015 former engineer Erica Baker made a spreadsheet showing pay disparities at the company. She detailed her quest in a Twitter thread.

Even though Google has released its methodology of determining compensation, Polli said "tech companies in general do have a blind spot when it comes to diversity."

For now, she said, "We're just waiting on the other shoe to drop," which may be finding out what exactly the Department of Labor knows."

"It definitely gets people's attention when they name names," Polli said. "And everyone is now hyper-focused on this issue. It's calling attention to the fact this pay disparity happens."