The department sent letters to parents who had submitted their children for its "Early Intervention Program" informing them the children may be at risk of identity theft as a result of the October break-in at the public storage unit, KTVK-TV in Phoenix reported Tuesday.
"The hard drives contained info that might include name, address, insurance info, child disability, date of birth and Social Security number," the letters stated.
A department spokesman said the hard drives, valued at $450, were all password-protected and the agency does not believe any of the information has been accessed.
"We don't have any reason to believe that DES and our computers were the target of theft," the spokesman said.
Police said they were seeking two suspects, a man and a woman, who are believed top have stolen the hard drives.