HONOLULU -- One of the state's biggest car insurance companies has begun charging more based on drivers' zip codes.

After a KITV investigation, the state said it will demand Progressive Insurance justify its rates.

The controversy over zip code-based rates for car insurance began when people in minority- and low-income neighborhoods on the mainland were unable to get fair-priced insurance. Now the question is: Is that happening in Hawaii?

An anonymous customer of Progressive Insurance had her annual premium rise $200. A Progressive agent told her is was because of her zip code.

"That's probably not a valid answer," state Insurance Commissioner J.P. Schmidt said.

The insurance commissioner said zip code-based rates have not been allowed in Hawaii, partly because of abuse on the mainland.

"One of the concerns is that there will be illegal discrimination," Schmidt said.

Drivers say it's unfair.

"It should be strictly based on your driving record and that's it," Mililani resident Harland Perry said.

Progressive's last rate filing set base rates for some neighborhoods higher than others. Two zip codes, 96712 in Haleiwa and 96762 in Laie, had the highest base rates.

"I don't think that's fair at all. I lived out there for seventeen years. I moved into town once for about two months and my truck got stolen while I was in town, so tell me about that," Hauula resident Jimmy Kruger said.

Seven others had the second-highest; only four zip codes had Progressive's lowest base rate. The difference from the highest to the lowest neighborhoods was about $100 a year.

The insurance commissioner is concerned.

"You've raised some issues that we feel we do need to look at, and we need to get some additional information on it to make sure that what this company is doing is appropriate," Schmidt said.

Progressive did not return calls by KITV on Friday. Insurance regulators doubt the company is using zip coding to illegally discriminate. They think it is more likely that a big mainland computer just spit out the rates without even knowing where the zip codes are.

The state said it will now force Progressive to justify its rates zip code by zip code.