TD Ameritrade had one of its databases hacked and contact information stolen on more than 6.3 million customers, according to the Associated Press.

More sensitive information such as Social Security numbers and account numbers does not appear to been stolen, a TD Ameritrade spokeswoman said.

The Omaha-based brokerage would not share many details of its investigation, including when the hack took place, because it still looking into the theft and is cooperating with investigators from the FBI.

Ameritrade customers have received unwanted e-mail ads because of the data theft. There is no evidence that any customer suffered financial losses or was a victim of identity theft, said spokeswoman Katrina Becker.

Ameritrade informed its customers on Friday and posted information on its website.

“While the financial assets our clients hold with us were never touched, and there is no evidence that our clients’ Social Security numbers were taken, we understand that this issue has increased unwanted SPAM, which is annoying and inconvenient for them,” said Chief Executive Joe Moglia.

Ameritrade said it is confident it identified how this information was taken and has changed its computer code to prevent the theft from recurring. The brokerage added that any new client who opened an account after July 18 was not affected.

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