Hackers from China infiltrated the Web site of the Pennsylvania state government, but officials said they found no evidence of damage.
Four state departments had security problems with their Web pages, leading to a decision to take down nearly all of the state's Internet site on Friday morning.
Office of Administration spokeswoman Mia DeVane said there was no reason to think anyone's personal data had been compromised or that any damage occurred when a hacker "got into what we would say is a back door."
By late afternoon, nearly all of the state's site had been put back online.
"It was more that we needed to take down those sites to make sure a virus couldn't spread," she said.
The problems arose at pages of the departments of Labor and Industry, Education, and Military and Veterans Affairs, as well as the Pennsylvania Lottery's page.
Investigators tracked the source to a domain registered in China, she said.
It is not unusual for the state's computer system to be the target of hackers, but having problems at four separate branches of state government prompted the decision to take down nearly the entire system, she said.
DeVane said Pennsylvania's information technology officers learned during a conference call held by the Multi-State Information Sharing and Analysis Center that four other states and one state university had been attacked in a similar manner.