LIHU'E, Kaua'i — A miniature data drive missing from Wilcox Memorial Hospital contains the names and Social Security numbers of every person who has been a patient at the hospital for more than a decade, and hospital officials are warning patients of a possible security breach.

There has been no indication it has been used for fraudulent purposes, and it is not entirely clear whether the drive was stolen or mislaid, the hospital said.

The drive was reported missing Oct. 5 from a secure area in the hospital. It contains data on 130,000 patients who have been served by the hospital for the past 12 years, said Lani Yukimura, Wilcox public information officer.

The hospital has written its patients to warn them that it is possible the information was stolen, although it is not clear that is the case. What the hospital knows is that a tiny data drive — sometimes called a thumb drive or USB flash drive — is missing. The drive was used as a backup for accessing patient data when the hospital's main computer system malfunctioned, Yukimura said.

Such drives are typically inserted into a computer's USB or universal serial bus port. They are roughly the size of a pack of chewing gum strips, about 3 inches long, 3/4 inch wide and 1/3 inch thick. They are designed to be portable, and are often fitted with a lanyard so they can be readily carried around the neck.

"Our ongoing internal investigation has been thorough but has not produced either the drive or any leads as to where it might be. In the event that this was an act of theft, we have filed a report with the Kaua'i Police Department," hospital chief operating officer Cathy Clark wrote in a letter to patients.

She said the card included name, address, Social Security number and medical record number of patients, but no actual medical information. The hospital has taken new precautionary measures to better protect personal data in the future, she said.

One such security measure: The hospital is no longer using portable data drives.

While there is no evidence that the information has been used in any kind of identity-theft crime, the hospital has asked patients to be alert to any such use of their personal information.

Yukimura said the first letters alerting patients of the missing drive were received at midweek, and the hospital has received a few dozen calls asking for more details or thanking the hospital for warning them of the possible problem.

Reach Jan TenBruggencate at jant@honoluluadvertiser.com.