A laptop computer containing the personal information of more than 44,000 Cleveland State University students, previous students and applicants was stolen from the university's admissions office.
The university issued a statement Friday, a week after the computer was taken.
Information on most of the students included addresses and Social Security numbers and could reach back to student rosters 4 years old.
An investigation is under way, although officials believe the computer was stolen for the hardware rather than the data.
"We're thinking it's a crime of opportunity where someone just saw the computer and ran," CSU spokesman Brian Johnston said.
He would not discuss the circumstances because of the investigation. But CSU President Michael Schwartz issued a stern warning on the school's Web site urging staff to practice computer security measures.
CSU will notify the affected students in writing, Johnston said. The university will provide them with information on how to have credit bureaus flag their files with fraud alerts.
Anyone with questions may contact university enrollment officials at ed.mills@ csuohio.edu or 1-888-278-6446.