The U.S. Equal Employment Opportunity Commission has spent much of the past year investigating Uber for alleged gender inequality, according to a person familiar with the investigation.

The federal probe began in August and is exploring alleged unfair pay and other gender-based discrimination at Uber, said the person, who spoke on the condition of anonymity to discuss sensitive matters.

The investigation was spawned by a complaint from an employee about gender hiring practices and pay, according to the Wall Street Journal, which was the first to report on the probe. Investigators are interviewing Uber employees, reviewing the company’s hiring practices and “seeking documents from Uber officials,” the paper reported.

Citing confidentiality rules, EEOC spokeswoman Kimberly Smith-Brown said the agency is prohibited from confirming or denying the existence of investigations. The spokeswoman added that information only becomes public when the agency files a lawsuit.