A lost computer tape containing the names, addresses and Social Security numbers of 2 million residential mortgage customers of ABN Amro Mortgage Group was found on Monday, but the company continues to urge affected customers -- including an unknown number in the Pittsburgh region -- to sign up for a free credit monitoring service it arranged to help guard against possible identity theft.

The company, a subsidiary of Chicago-based LaSalle Bank Corp., said it was continuing to investigate the incident and that there have been no signs that the confidential data, which it first reported missing on Friday, was misused.

ABN Amro, based in Ann Arbor, Mich., sent notification letters to affected customers Friday. The company said the tape had been picked up at its Chicago data center by a shipping company, DHL, on Nov. 18, but did not arrive at its destination, an Experian credit bureau in Allen, Texas.

After searching for it for about a month, ABN Amro announced it was missing. Then on Monday, the company said the tape had been located by DHL and returned.

"We understand the concern that this incident may have caused and we deeply regret that it occurred," the mortgage company said on a special Web site set up to explain the incident, www.info.mortgage.com.

Customers who decide to enroll in the free credit monitoring service, provided by the credit reporting bureau TransUnion, should follow the instructions in their notification letter, the company said.

Customers who did not get a notification letter but would like to know whether their account information was on the tape, which also included mortgage payment histories, may call 1-800-783-8900 (select option two).

A spokesman for the mortgage company was unavailable for comment yesterday.

After the tape was lost, ABN Amro, one of the largest loan originators and servicers in the country, said it began electronically transmitting customer data.

Illinois is one of a growing number of states that has enacted laws recently requiring companies to notify customers of security breaches concerning sensitive personal data. The rush comes against a rash of high-profile instances of lost, misplaced or stolen data involving such companies as Citigroup, ChoicePoint, Bank of America and Lexis-Nexis.

A breach notification bill passed by the Pennsylvania Legislature last week is awaiting the governor's signature. But the pending legislation has been criticized by the Pennsylvania Public Interest Research Group as too weak, giving companies too much leeway in deciding whether to disclose a breach.