GoDaddy, a major hosting and domain registration service, says the websites and email accounts affected by a major outage Monday afternoon have been restored.

GoDadddy spokeswoman Elizabeth Driscoll told The Associated Press the outage began shortly after 1 p.m. EDT. By around 5:50 p.m., sites hosted by the company were back up and running.

GoDaddy, which hosts more than 5 million websites, said it’s investigating what caused the crash.

Twitter user @AnonymousOwn3r, a self-described “official member” of the hacking collective Anonymous, is claiming responsibility for the apparent cyber attack.

“I'm taking godaddy down bacause well i'd like to test how the cyber security is safe and for more reasons that i can not talk now (sic),” @AnonymousOwn3r tweeted in response to another user.

@AnonymousOwn3r said the attack was not part of a broader Anonymous hack.

Anonymous gained notoriety by shutting down various U.S. government sites in response to anti-online piracy legislation.