Ameriprise Financial, an investment group part of American Express until last year, said the personal information of nearly a quarter-million clients was compromised last month.
The investment advisory firm said that a laptop computer containing the personal information of about 230,000 customers was stolen from an employee's parked car, according to numerous media reports. The breach, which occurred in late December, affected reassigned customer accounts being stored unencrypted, according to a report in The New York Times.
Ameriprise has sent letters to all customers affected by the breach. The company also said in a statement that it is not aware of any criminal use of breached data.
"We take our responsibility to safeguard personal information very seriously. Although the risk of misuse of the data contained in these files is very low, we apologize for any inconvenience or concern this situation may cause," said Brian Heath, president of Ameriprise's U.S. Advisor Group. "We have made every effort to notify affected individuals and to make them aware of the situation and the steps we are taking."
A company spokesperson said that it was unlikely that the thief knew the contents of the laptop, according to numerous reports.
Ameriprise is the latest in a list of companies and organizations to suffer a major data security breach that includes the University of Southern California, ChoicePoint, Bank of America and the U.S. Air Force.
Earlier this week, the University of Notre Dame said a hacker may have gained access to images of donor checks sent to the college after the breach of one its online servers earlier this month.
The South Bend, Ind., university said it had not received any reports of personal information used for nefarious purposes.