An investigation has found 30 percent of the inmates at a Heartland jail were illegally collecting food-stamp benefits.

Federal rules prohibit people from collecting the benefits while behind bars for 30 days or more. But Iowa doesn't routinely check on compliance.

The Iowa Department of Inspections and Appeals last March checked the names of the 519 inmates at the Polk County jail. It found 30 percent, or 157 inmates, were illegally collecting food-stamp benefits, now accessed via an electronic card.

Some inmates gave their cards to others, while others sold theirs.

The Iowa Department of Human Services administers the food-stamp program. Spokesman Roger Munns says when the agency is informed a person has been in jail for more than 30 days, the benefits are canceled.