MONMOUTH — Police are warning of a scam involving bad checks that appear to be from a legitimate company.

Monmouth police Officer Dana Wessling said the scammers have stolen a bank account number for Tuscon, Ariz.-based R&R Products that they include on forged bank checks used to buy items for sale on Internet sites.

An R&R representative said the check number connected to the account can only receive payment from customers, according to Wessling.

“He says his bank is getting 1,000 of these a day from all over the United States,” Wessling said. He has not heard of other checks being distributed in Maine.

The scam came to light when a Monmouth resident posted a Craigslist ad for tires. He was asking $125, but the fraudulent buyer sent a check bearing the R&R name, address and bank account was made out for nearly $2,000.

The “buyer” asked the seller to cash the check, keep $150 for his trouble, then mail the rest back to the buyer.

In this case, the buyer sensed trouble and went to Monmouth police, but the scammers hope the seller will send the refund before the bank that cashed the checks learns it is no good.

Wessling said other people receiving the fake R&R checks are shipping the items they are selling, only to learn later that the checks are worthless.

Wessling urged people never to send refunds on oversized checks and to wait until a check clears before shipping a product.

“Even if their success rate is 10 percent, they’re making a lot of money,” Wessling said.