DALLAS —  Consumer groups are warning about the proliferation of payday loan stores (search) and are urging customers to be aware of the risks involved in short-term, high-interest borrowing.

The number of loan stores has more than doubled in the past four years and the businesses are trying to shed their old image as sleazy, dirty outposts in shady locations.

FastBucks (search), one of the fastest growing chains, offers ATM-style debit cards and, along with coffee and candy, hopes to bolster its image.

"We have crisp, clean operations with well-trained employees that give excellent customer service," FastBucks CEO Charles Horton said, pointing out that many of his customers are college-educated and middle- to upper-income earners.

But consumer advocates say the new images shouldn't distract borrowers.

"Payday loans are a debt trap because consumers get started and have trouble paying off the loans out of their next paycheck," said Jean Ann Fox of the Consumer Federation of America (search).

Each state has its own regulatory system on payday loan stores. In Arkansas, the attorney general is investigating more than a dozen payday loan stores.

Click in the video box above to watch a report by FOX News' Phil Keating.