According to Eyeteeth, the grassroots petition Web site Change.org has confirmed that it has been hit by a denial of service attack, most likely in connection with its hosting of a “Human Rights Petition” for the release of Chinese artist Ai Weiwei.

“The distributed denial of service (DDoS) attack began early Monday and made the site completely inaccessible for a few hours,” the Web site said in a statement. “Change.org issued a formal request for urgent assistance to the U.S. State Department’s Bureau of East Asian Pacific Affairs within hours of the attack.”

“We do not know the reason or exact source of these attacks,” Ben Rattray, the founder of Change.org, added in the statement. “All we know is that after the unprecedented success of a campaign by leading global art museums using our platform to call on the Chinese government to release Ai Weiwei, we became the victims of highly sophisticated denial of service attacks from locations in China.”

The petition was spearheaded by the Guggenheim museum, and has continued to draw support from some of the biggest leaders in the museum world, from Glenn Lowry of MoMA and Michael Govan of LACMA, to Yongwoo Lee, president of the Gwangju Biennale Foundation, and Manray Hsu, founding director of the Taipei Contemporary Art Center.

As of this writing, the petition — which Change.org says has been attracting some 10,000 signatures a day, and now has 92,000+ signatures — is back online.