OKLAHOMA CITY (AP) — A storm system that produced a deadly tornado in Oklahoma has moved into the central plains and remains a threat to produce another round of tornadoes across the nation's midsection.

Bill Bunting — chief of operations at the National Weather Service's Storm Prediction Center in Norman — said Sunday that the system was centered over Nebraska and would move easterly as the day progressed.

He said it has weakened slightly — but could produce tornadoes Sunday in an area from the Great Lakes to Louisiana. Bunting said the greatest threat appears to be from northeastern Iowa to southeastern Minnesota and into western and central Wisconsin.

The system produced a tornado that killed five people in northwestern Oklahoma early Sunday. Bunting said there have been 121 reports of tornadoes spawned by the system — but that number isn't confirmed.