Data privacy regulators in the US are opening legal proceedings within a broader probe into allegations of gender bias at American computer games developer, Riot Games.

The California-based software company and e-sports tournament organiser is behind unforgettable industry titles such as Super Zac Ball, Cho'Gath Eats the World, and Ziggs Arcade Blast.

Now the California Department of Fair Employment and Housing (DFEH) is looking for proof to back up suspicions that Riot Games is paying more money to male employees than female.

The organisation also said it would be investigating the possibility of pay and promotion discrimination at the company, as well as accusations of sexual harassment and assault.

If successfully, the enforcement action submitted against Riot Games by the DFEH will see the games developer give up data on workers’ wages. As of yet, the DFEH says, Riot has not cooperated with the regulator and has not given sufficient information regarding potential pay discrepancies.

Speaking to the Verge news website, Riot Games claimed it had responded “promptly” to the requests made by the DFEH, and that it had handed over more than 2,500 pages of documentation along with “several thousand lines of pay data”.

The statement by Riot added:

“We've been in active conversations with the DFEH since its inquiry began. Investigations like this can arise when there have been allegations of workplace disparity and we've been co-operating in good faith with the DFEH to address its concerns.”

Riot expressed its disappointment at the DFEH saying that cooperation had not been forthcoming.

Reports of the probe come after a walkout staged in May regarding the way in which Riot Games dealt with accusations of gender bias. The occasion saw around 150 staff members walk out after legal action was taken by the company to prevent two women from suing for discrimination.

Riot Games said that the women involved had waived their right to sue as part of their contract of employment.