Google's investigation of a cyberattack that rocked the company's infrastructure in mid-December includes a probe of its staff in China, a source familiar with the investigation said on Monday.

The U.S. search giant last week said it had uncovered a "highly sophisticated and targeted attack" coming from China on its infrastructure that resulted in some of its intellectual property being stolen, Google said in a blog post.

The attack on Google's servers in December targeted the Gmail accounts of Chinese human rights activists. Google said it had decided to stop censoring search results in China, which could lead to the shutting down of the search engine and operations there.

Google is considering possible employee involvement in attacks as part of a thorough investigation, the source said. However, Google does not consider the attack an inside job, as 20 other companies were affected by similar intrusions originating from China, the source said. Companies including Adobe and Juniper have said they were targets.

Google has a couple hundred employees in China. Employees there got an optional day off on Tuesday last week as the network was scanned and tested for inconsistencies. The network has been running and active for the last few days.

Google officials declined comment on the topic.