Federal regulators determined that a pet food company improperly tested or failed to test corn shipments for a deadly fungus that has been blamed for deaths and illness in dozens of dogs, a newspaper reported Monday.

According to a government report obtained by The (Columbia) State, the U.S. Food and Drug Administration found that Diamond Pet Foods allowed tainted corn into its Gaston plant and failed to properly test for the naturally occurring poison aflatoxin.

The federal agency began an investigation after the company recalled about 1 million pounds of dried dog food on Dec. 20, said FDA investigator Phil Campbell.

The report, expected to be released this week, represents the agency's findings but does not penalize the company, the newspaper reported.

A spokesman for the FDA did not immediately return a call Monday from The Associated Press seeking comment.

Diamond Pet Foods spokeswoman Carol Anderson said the company is cooperating with the investigation. It has improved its testing of incoming corn and is checking its final product before shipping, she said.

Southeastern states tend to have a higher occurrence of aflatoxin because of the region's hot, humid summers, experts say. Typically, the company gets one or two tainted loads of corn each year, but beginning in September, the tests began showing one or two tainted loads a week, company officials said.

Dozens of dogs in eastern and southern states have died or become sick from aflatoxin poisoning after eating the tainted food.