The hard drive containing computer backup data was reported missing from Wilcox Memorial Hospital on Oct. 5, said Lani Yukimura, a spokeswoman for Wilcox Health. Letters went out Monday to the patients affected by the missing data, she said.

The data file, which included names, addresses and medical record numbers, as well as Social Security numbers, was contained on a small, portable hard drive called a "thumb drive," she said. It did not contain medical records.

"While our systems are extremely secure, our employees are trained and we have procedures in place, this incident showed us that we need to have clearer policies on both encryption as well as access to backup data," she said. "We have discontinued the use of thumb drives for this type of information storage."

The information was not encrypted and could be read using Adobe Acrobat Reader.

"We have no indication anyone has used this information," she said. "It is missing, and we want people to know about it," Yukimura said.

Hospital officials waited 12 days to notify patients about the missing hard drive because they wanted to make sure the drive was indeed lost, said David Fox, information security and privacy officer for Hawaii Pacific Health, the hospital's parent company.

"We didn't want to sit on it any longer based upon the respect we have for the patients, and the risk it could potentially create."