Nocturnal tornadoes tore through Oklahoma, where the governor signed an executive order on Sunday declaring a disaster emergency. There were reports of injuries and at least four deaths.

The National Weather Service’s Storm Prediction Center said there’s an enhanced risk for severe thunderstorms between Tuesday and Wednesday, with “large hail, severe gusts and a few tornadoes possible” from western and central Iowa to northeastern Kansas.

The storms, part of an outbreak of severe weather across the middle of the U.S., began in Oklahoma late Saturday and killed four people, including an infant, and left at least 100 others injured,