WASHINGTON - A Minnesota company that processes loans for students nationwide has reported a major theft of "personally identifiable information" involving 3.3 million students after a break-in last weekend at its Oakdale headquarters.

Officials at the company, ECMC, say it could be one of the biggest cases of student identity theft in the nation, affecting 5 percent of all students with federal loans in the United States.

ECMC, founded 16 years ago as Educational Credit Management Corp., said Friday that the stolen data include names, addresses, dates of birth and Social Security numbers. No bank account or other financial information was included in the data.

In an e-mail Friday to several members of Congress that was obtained by the Star Tribune, company chief executive Richard Boyle said the theft occurred from a "secured location at ECMC involving portable media with ECMC student loan borrowers' personally identifiable information."

According to Boyle, the company is "not aware of any instance of this data being misused."

Congressional sources said the data were stored on discs contained in a safe.

Oakdale police Capt. Jack Kettler would not comment on the case, saying the Minnesota Bureau of Criminal Apprehension is leading the investigation. But BCA spokeswoman Jill Oliveira said that while Oakdale police have called the BCA's financial crimes task force, local police are still in charge.

A spokesman for the U.S. Department of Education, which was notified Wednesday, said the FBI also has been brought into the case. "Protecting student privacy is a top priority," said spokesman Justin Hamilton.

ECMC officials said they discovered the theft Sunday afternoon and immediately contacted police. The break-in is believed to have occurred either Saturday or early Sunday.

The theft was not publicized until Friday at the request of law enforcement, said David Hawn, ECMC's chief business development officer. He said "we simply do not know" if the student data were the target of the theft.

"We deeply regret that this incident occurred and the stress it has caused our borrowers and our partners, and are doing everything we can to help protect our borrowers' identity and personal information," Boyle said in a statement released Friday.

The company said it has arranged with Experian, a leading national credit protection agency, to provide affected students with free credit monitoring and protection services. The company is sending letters to affected students with information on fraud protection and identity theft insurance coverage.

"I want to emphasize we are taking this incident very seriously and it is our top priority that our borrowers are informed and supported," Boyle said in his e-mail to Congress.

ECMC is one of the top 10 student loan guaranty agencies in the country, according to its website. The nonprofit corporation guarantees federally backed student loans, meaning that if a loan isn't paid back, ECMC makes the lender whole. The company also services student loans that have fallen into bankruptcy, and is the U.S. Department of Education's designated handler of bankrupt student loans.

The company had long been based in St. Paul. In 2008 it moved its headquarters -- and 320 jobs -- to Imation's campus in Oakdale.

Federal education officials said the case ranks among the more serious identity theft cases of modern times, among them a data breach at the U.S. Department of Veterans Affairs in 2006 that affected 28.6 million people, and a Bank of America credit card breach in 2005 that exposed 40 million accounts.

The theft exclusively involved data from ECMC customers. The company said it would set up a toll-free telephone hotline Saturday at 1-877-449-3568. Borrowers can also go to the company website, www.ecmc.org.

Staff writers Sarah Lemagie and Mike Hughlett contributed to this report. Kevin Diaz is a correspondent in the Star Tribune Washington Bureau.