Australia's first attempt to conduct a census online was in disarray after several cyberattacks on the website, an official said Wednesday.

The Australian Bureau of Statistics shut down the site to protect data on Tuesday night after four denial-of-service attacks that came from somewhere overseas, chief statistician David Kalisch said.

"It was an attack," Kalisch told the Australian Broadcasting Corp. "It was quite clear it was malicious."

The 2 million Australians who managed to access the site on Tuesday before it was shut down were assured that their private data was secure.

"There has been no attack on the information, it was an attack on the system. The information is secure and safe," Kalisch said.

Australia's Privacy Commissioner Timothy Pilgrim said in a statement he was investigating the cyberattack "to ensure that no personal information has been compromised."

Australian security officials were attempting to determine the source of the attacks, Kalisch said.

Kalisch said "a gap" in the digital defenses of the bureau of statistics had been fixed and the site would be reopened Wednesday.

The census is conducted every five years. The decision to conduct the national survey online and to keep the information for four years before it was destroyed instead of the usual 18 months heightened privacy concerns this year.

Several senators announced that they would risk fines by refusing to include their names and addresses in their census forms. Officials attempted to allay fears by boasting that the bureau of statistics had never been hacked.

The site was shut down after a fourth cyberattack Tuesday evening, and people who telephoned the bureau of statistics for an explanation were told by a recorded message to call back on Wednesday.

While the census focuses on people's circumstances on Aug. 9, forms started to be accepted a week before that date and will continue to be until September. Traditional paper census forms were provided to householders on request.

Conducting most of the survey online was estimated to save 100 million Australian dollars ($76 million).

-AP