Identity thieves allegedly used debit cards to make fraudulent donations to the presidential campaign of U.S. Rep. Ron Paul.

Campaign staffers spotted several hundred $5 charges from similar Internet addresses this month. Security officials for San Antonio-based Frost Bank noticed a similar pattern on check cards from an out-of-country location around the same time.

Fewer than 100 cards had unauthorized charges on them, and fewer than 500 cards were affected. Frost Bank refunded the money and canceled the affected cards.

"It's unfortunate whenever it happens, but our campaign and Frost Bank took rapid action," said Jesse Benton, a spokesman for the Texas Republican candidate's campaign.

The fraudulent donations, first reported by CBSnews.com, amounted to about $3,000 and were returned.

Bank officials said the identity thieves may have used the Paul campaign as a test to see whether the stolen debit card numbers were valid before attempting larger purchases.