NEW YORK, USA: Recent cyber attacks on Google and other American corporations have been traced to a top Chinese university as well as a school with ties to the Chinese military, the New York Times reported on Thursday, citing people involved in the investigation.

Those people told the Times that the Chinese schools involved are Shanghai Jiaotong University and the Lanxiang Vocational School. They said the attacks may have started as early as April 2009 - earlier than previously thought.

According to the report, investigators believe there is evidence suggesting a link to a computer science class at the vocational school taught by an Ukrainian professor.

Google jolted U.S.-China ties with its January 12 announcement that it had faced a "highly sophisticated and targeted attack" in mid-December, allegedly from inside China.

More than 20 other companies were also targeted, though Google said a primary target was dissidents' email accounts.

Jill Hazelbaker, Google's director of corporate communications said that the company's investigation is ongoing, but otherwise declined to comment.

The Chinese schools were not immediately available for comment, but the New York Times said they had not heard that American investigators had traced the Google attacks to their campuses.