The Social Security numbers, home addresses and phone contacts for at least 300 students who applied for admission to Cal Poly Pomona six years ago were unintentionally disclosed online, according to the university.
The personal information remained on the university server and accessible to the public for about five years, school officials said.
The applicants were notified last week and urged to contact credit reporting agencies, school officials said.
The personal information, which did not include financial data, "was mistakenly put in a publicly accessible folder on a university server in November 2003, and Google and other search-engine companies mined the data, according to a statement released by Tim Lynch, senior media communications coordinator for Cal Poly Pomona.
Lynch said a maximum of 355 applicants could have been affected.
The file containing the applicants' data was removed from the university server in November 2008, when it came to the attention of university officials that it was publicly accessible, Lynch's statement said.
But school officials were unaware that "some of the contents of the file were retained in keyword indexes maintained by Google," it added.