The US Equal Opportunity Commission began the probe in August of last year focusing on whether women at Uber were treated the same as their male counterparts when it came to pay or opportunity at the San Francisco-based startup, according to the source.

The source indicated Uber is one of several Silicon Valley firms being reviewed for potential gender discrimination.

The probe began as Uber ousted its chief executive in response to a series of missteps and revelations about a toxic workplace culture and ethically dubious business practices at the global ride-hailing giant.

"We are continually improving as a company and have proactively made a lot of changes in the last 18 months," an Uber spokesman said in response to an AFP inquiry.

Changes made at Uber include a new salary structure; an overhauled performance review process, and diversity training for company employees worldwide, according to the spokesman.

Uber in May was hit with a lawsuit in California alleging sexual harassment and discrimination against female employees, apparently the first case in court since the ride-hailing giant scrapped a requirement for arbitration of such claims.

The suit filed in California superior court contended the company work culture was "permeated with degrading, marginalizing, discriminatory, and sexually harassing conduct towards women" and that this was perpetuated and condoned by managers.

Uber chief executive Dara Khosrowshahi was hired last year to lead the company after its image was battered by a litany of controversies about a cutthroat workplace, sexism, and unscrupulous tactics with regulators and rivals.

Uber launched an "urgent investigation" after an engineer who worked at the company until late 2016 alleged that her manager made sexual advances shortly after she joined.

She wrote in a blog post that she complained to more senior managers and the company's human resources department, but was told that it was the man's "first offense" and that they wouldn't feel comfortable punishing a "high performer."

The woman said she met other female Uber engineers who said they had experienced similar harassment.

Uber hired former attorney general Eric Holder to review workplace conditions after the allegations. The probe resulted in firings and an outline for needed changes.