Twister outbreak: At least 31 tornadoes tear through U.S. this week

The tornado that ravaged a county in Delaware on Saturday night was one of many that have torn through the U.S. this week.

Experts say this latest incident is among at least 31 confirmed tornadoes since Friday.

It's an outbreak of twisters that stretched across nine states.

The most powerful one was an EF-4 in Iowa on Friday. It delivered winds topping off at 170 mph.

Also on Friday, a tornado buckled a roof in Illinois. It collapsed onto a packed concert venue, killing one person and injuring several more.

That was an EF-1 tornado, which experts said traveled 27 miles before winding down.