The San Francisco-based bank on May 5 posted a statement on its Web site saying that the computer, which belonged to its mortgage group, was reported missing while being transported between Wells Fargo facilities by an undisclosed global express shipping company.

The company did not disclose when it discovered that the computer was missing.

The stolen system contained various types of customer data, such as names, addresses, Social Security numbers and mortgage loan account numbers, the company said in the statement.

So far, there's no indication that the information kept on the computer has been misused, said a company spokesman. According to the company's statement, "the computer has two layers of security, making it difficult to access the information."

Wells Fargo is currently sending letters to inform individuals whose data was stored on the computer about the incident. The letter also advised the affected customers and prospects of what steps they can take to mitigate exposure to identity theft. The company said it will pay for a one-year subscription to a credit-monitoring service for affected individuals.