TACOMA, Wash. -- At least 75 people have fallen victim to a "highly organized" group of thieves who used skimmers to steal debit card information and drain money from Pierce County residents' bank accounts, officials said.

Sheriff spokesman Ed Troyer said the skimmers were placed on gas pumps at the Arco gas station at 11608 Meridian on South Hill in August 2007, but the crooks didn't use the card data until the July 4th weekend.

The skimmers are electronic devices designed to look like part of the payment system at gas pumps and ATMs, but actually secretly record card numbers and PINs for later retrieval by the thieves. They're often attached on top of the real card readers.

Troyer said the thieves likely waited to use the bank information until the long holiday weekend in an effort to delay detection of the thefts.

The fraudulent cards made from the data collected by the skimmers were used at bank ATMs throughout King County to withdraw thousands of dollars from each account.

Some account holders lost as much as $4,000, and the total loss added up to hundreds of thousands of dollars, Troyer said.

Investigators believe there are many more victims and urged anyone who used a debit card at the Arco station to contact their bank to get a new card.

A reward is being offered for information leading to an arrest, and the sheriff's office released security camera photos of people using the stolen information to make withdrawals.

Anyone with information is asked to call Crime Stoppers at 253-591-5959.