Ride-hailing firm hired former US attorney general Eric Holder and Tammy Albarran to conduct review of allegations.
Uber Technologies Inc said it has extended its internal investigation into sexual harassment claims in its own organization, and a report is expected by the end of May.
In February, Susan Fowler, a female former engineer at Uber, said in a widely read blog post that managers and human resources officers at the company had not punished her manager after she reported his unwanted sexual advances, and even threatened her with a poor performance review.
Board director Arianna Huffington, in a memo to employees on Thursday, said the board subcomittee has granted a request for more time to complete the assessment and the investigation is being extended to "ensure that no stone is left unturned".
The memo states that the internal report is anticipated by the end of May.
The ride-hailing firm hired former US Attorney General Eric Holder and Tammy Albarran, who are partners at the law firm Covington & Burling, to conduct a review of the claims as well as general questions about diversity and inclusion.
According to Recode, Holder has not had the opportunity to interview several key figures in the investigation, including top human resources executives. He plans to do so in the coming weeks.
Uber has come under more pressure over the results of its sexual harassment review, particularly after the scandal at Fox News leading to the ouster of its anchor Bill O'Reilly.
Chief Executive Travis Kalanick called the allegations by Fowler "abhorrent and against everything Uber stands for and believes in".