A California blood bank has retrieved a stolen laptop, but remains concerned that some donors could be at risk of identity theft.

Delta Blood Bank, based in a Stockton, California, paid a reward for the Compaq laptop, which had been stolen after a 10 December blood drive in the nearby town of Tracy. On 15 December, the blood bank notified more than 100,000 donors that their personal information had been filched and warned them of the threat of identity theft.

With the problem of identity theft spiralling out of control, California last year passed a law requiring organisations to notify state residents if their personal information was compromised. In accordance with that law, Delta sent out more than 100,000 letters to donors whose names, dates of birth, Social Security numbers and other key information was contained in a database on the laptop.

Even with the laptop back in its possession, the blood bank reiterated that warning on Wednesday.

"The suggested precautions in the letter still stand," said Arthur Morrison, marketing director for the blood bank. "Donors should still put a fraud check on their credit report, which they can do free."

Delta said it retrieved the computer on Tuesday night after paying a $1,500 reward. Following the theft, the blood bank had circulated posters in Tracy offering the reward with "no questions asked".

The laptop is now in the hands of a forensics expert who will try to determine whether or not the database was accessed or copied, Morrison said. The blood bank believed the laptop was stolen for its hardware rather than for the information it contained, he added, noting that the computer's security features offered some protection to the sensitive data.

Laptop theft has emerged as a chronic threat for banks, blood banks and other institutions that collect personal information. Wells Fargo has grappled with several such breaches. In June, a computer theft at the University of California at Los Angeles exposed more than 145,000 blood donors.

Negative publicity about the Delta theft comes at a difficult time of year for blood banks, Morrison said. With the bustle of the holiday season, donations typically dwindle.

But Morrison sounded an optimistic note that the theft wouldn't further deter potential donors.

"Nobody wants their credit tampered with," he acknowledged. "But blood donors are really special folks. They want to save lives. I don't think they're going to say, 'No, I'm not going to save a life today.' If they go away at all, I think they'll come back."