The servers hosting Blizzard's popular World of Warcraft, Hearthstone and Overwatch games are having problems for the second time in three days, leaving customers unable to login.

Games developer Blizzard has confirmed once again that the problem impacting its servers is related to authentication. "We're currently investigating an issue affecting our authentication servers, which may result in failed or slow login attempts," the company's customer support said on Twitter Monday.

The latest problem comes just days after a similar outage impacted players in North America and Australia for several hours Friday. According to a heat map on the Down Detector website, most complaints this time are coming from the U.S. West Coast, Australia, Japan and Europe.

The fact that the company is dealing with a second outage in such a short space of time could suggest that the problems are the result of a malicious attack on the platform, though no one has claimed responsibility for any such attacks.

In April, the company said it was battling a distributed denial of service attack that was preventing its customers from playing their games, and that attack was claimed by the hacking group called Lizard Squad. Lizard Squad has previously carried out attacks against World of Warcraft in 2014 and is also credited with attacking both the PlayStation Network and the Xbox Live systems.