The U.S. Postal Inspection Service did not return calls and e-mail messages seeking comment Friday.

LexisNexis has tightened up the way it verifies customers since the incident, the company said in the notification letter.

LexisNexis was involved in other data breaches in 2005 and 2006, according to from Privacy Rights Clearinghouse, a privacy watchdog group.

According to CBS News, which the breach, another company, Investigative Professionals, was also hit by the scammers, who were ultimately able to obtain information on 40,000 victims, including those targeted using the LexisNexis data.

Investigative Professionals could not be reached for comment.