More than 20 employees have been fired from Uber as part of an internal investigation, a company spokesperson told CNBC, after a former employee alleged gender bias and sexual harassment within the start-up.

In an explosive blog post earlier this year, former Uber engineer Susan Fowler alleged the company failed to act on sexual harassment and gender discrimination complaints. CEO Travis Kalanick called for an urgent investigation into the claims.

Now, San Francisco-based Uber's 14,000 employees have been given an assessment of the probe led by law firm Perkins Coie.

The firm examined 215 claims at Uber, and took no action in 100 instances, a spokesperson said. Not all these claims involved sexual harassment — they also included retaliation, discrimination and other issues. The 20-plus terminations also were based on a variety of claims, according to the spokesperson.

Separately, a source told CNBC that the firings included employees at all levels, including high-level employees. But Kalanick was not in attendance when the firings were announced, as he is with family in Fresno, California, the wake of a tragic accident and death in the family.

A separate investigation is being led by former U.S. Attorney General Eric Holder. An executive summary of the report from Holder will be discussed at the all-hands meeting next Tuesday, a spokesperson told CNBC.

Kalanick has not seen Holder's report, a source said.

Bloomberg's Eric Newcomer was the first to report the news of the firings on Twitter. Perkins Coie did not immediately respond to a request for comment.

View the tweet here

Fowler tweeted immediately after the release of the news, citing Uber insiders like Arianna Huffington and Liane Hornsey, head of human resources at the start-up, who had said the company did not have systemic problems with sexism.

Arianna and Liane to press: there is no systemic sexual harassment, just Susan. External lawyers: there are 215 cases of sexual harassment.

Sexual harassment has not been the only complaint about Uber's leadership. The company also has been criticized for its political ties in recent months, as well as run-ins with drivers and conflicts with regulators.

Kalanick has reportedly made a series of high-profile hires and may still be looking for a chief operating officer amid the fallout.

— CNBC's Deirdre Bosa contributed to this report.