State monitors will be working this week in the three offices of a western North Dakota insurance agency whose owner allegedly siphoned off more than $300,000 in customer premium payments.

Insurance Commissioner Jim Poolman said Sunday the monitors will be taking calls from Cottingham Insurance customers and verifying whether they have coverage.

The independent agency, which has offices in Bismarck, Underwood and Washburn, has hundreds, if not thousands, of customers and represented a number of insurance companies, Poolman said.

Cottingham Insurance's owner, Diane Cottingham, was found dead Saturday in rural McLean County near Max. McLean County Sheriff Don Charging did not respond Sunday to telephone and e-mail messages asking for comment on the case.

Cottingham was suspected of keeping some customers' insurance payments rather than forwarding them to the insurance companies, and forging documents to trick the customers into believing they were covered.

Poolman said he was unsure how many customers were affected.

"It's been a longstanding agency for almost 20 years, and so her book of business is large," he said. "It's going to take us some time. We're asking that people be patient, because we want to, as the Insurance Department, independently verify that there is coverage for each one of those policyholders."

The Insurance Department was tipped last week that something was amiss. Poolman said Cottingham admitted that a group of western North Dakota Cenex stations, which believed they had liability coverage through Cottingham's agency, had gone without insurance for four years.

Cottingham paid the stations' claims herself to conceal the fraud, Poolman said. She had agreed Saturday to sign an order revoking her insurance license, but missed an appointment to do so.