MADISON, Wis. (AP) _ Product pricing errors at a large discount store chain that used electronic price scanners has prompted the state to probe other stores for similar problems, Attorney General Donand Hanaway said Wednesday.

State investigators announced Wednesday that a November investigation of ShopKo Stores Inc. outlets in Wisconsin found scanned prices at the checkout counter sometimes failed to match the advertised sale price on store shelves.

Shopko, a Green Bay-based retailer with more than 90 outlets in Wisconsin and the Midwest, cooperated with the probe and has agreed to offer rebates of $1 to $5 to customers who discover future overcharges, Hanaway said.

Gene Bankers, vice president of ShopKo, said the company had taken steps to prevent future overcharges.

Hanaway said the investigation found 33 electronic pricing errors out of 270 items checked at 12 ShopKo outlets. Twenty-one of the errors involved overcharges, ranging from 2 cents to $9.99, while undercharges ranged from 2 cents to $5, he said.

Hanaway said most of the pricing errors resulted because the electronic price scanners were immediately reprogrammed after a sale but the sale signs not removed from shelves.

The attorney general said the overcharges ''were human errors and not an attempt to defraud customers,'' but the 12 percent error rate still was unacceptable.

''It's my suspicion that it's not just ShopKo,'' Hanaway said. ''It's much bigger than that.

''I am broadening the investigation to other general merchandising stores and food stores in the state to determine if pricing errors are occurring elsewhere,'' he said.

John Gary, spokesman for the National Retail Federation in New York City, said he did not know of any nationwide problem with electronic scanning of sale items.

''This is the first time I've ever heard of this kind of thing,'' Gary said.

Bankers said to avoid future problems ShopKo planned to put the expiration date of sales on all in-store advertisement signs.

Hanaway said he believed the ShopKo probe was ''the first in Wisconsin and, we believe, the nation,'' he said. ''We know of no one else who has undertaken such an extensive investigation.''

Steve Nicks, director of the state Consumer Protection Agency, said similar checks may have been conducted on the local level at individual stores.