Keystone Mercy Health Plan and AmeriHealth Mercy Health Plan said Tuesday that a portable computer drive containing the names, addresses, and health information of 280,000 Medicaid members in Pennsylvania has been lost.

The affiliated companies together insure 400,000 people on medical assistance in Pennsylvania.

The companies said the portable computer hard drive, used at community health fairs, was lost within the companies' corporate offices. Keystone's headquarters is in Southwest Philadelphia and AmeriHealth Mercy's is in Harrisburg.

The computer drive included members' health plan identification numbers and some of their health information, the insurers said.

Also stored on the drive were the last four digits of 801 members' Social Security numbers, plus complete Social Security numbers for seven others.

"We deeply regret this unfortunate incident," said the affiliates' president, Jay Feldstein, in a statement released by the insurers.

"We take our responsibilities for safeguarding personal health information very seriously. We have taken immediate steps to strengthen our operational protections to ensure this doesn't happen again," he said.

Feldstein heads Pennsylvania Managed Care Plans, Keystone Mercy Health Plan and AmeriHealth Mercy Health Plan.

The insurers did not respond to numerous requests for information, including questions about when and where the incident took place, whether any complaints have been received, and which regulatory agencies have been notified.

The insurers said they have beefed up security practices and will provide free credit-monitoring assistance to the people whose Social Security numbers, either in whole or in part, were on the missing hard drive.

The two insurance companies are jointly owned by Mercy Health System and Independence Blue Cross.

Keystone Mercy insures 300,000 medical assistance members in Philadelphia, Bucks, Montgomery, Delaware and Chester Counties. AmeriHealth Mercy's 100,000 members are in 15 counties in the Harrisburg, Allentown and Northeast Pennsylvania regions.