MARYLAND HEIGHTS, Mo. (AP) — Shoppers at Schnucks grocery stores are being encouraged to pay with cash or checks until a credit card fraud problem is resolved.

The St. Louis Post-Dispatch ( ) reports that investigators have received several complaints about credit card fraud linked to stores operated by the grocery chain based in Maryland Heights, a St. Louis suburb. Most Schnucks stores are in the St. Louis metropolitan area.

Schnuck Markets Inc. said last week that it has hired an outside forensics company to investigate.

Maryland Heights detective Sean Fanning cites at least 30 reports about unauthorized credit card charges, mostly from people who recently shopped at Schnucks. In some cases, transactions reached the thousands of dollars.

The Missouri Attorney General's office is also reviewing complaints from consumers.