Greenfield, Iowa tornado rated an EF-4

Survey teams have rated the tornado that ripped through a small Iowa city, leaving four people dead, as an EF-4 storm.

Officials say the tornado was on the ground for about 44 miles, with peak winds between 175 mph and 185 mph, tracking northeast, losing strength shortly after ripping through the City of Greenfield.

The National Weather Service says further "refinement" is possible, so the rating could increase. On Wednesday, crews said they had found evidence of at least EF-3 damage before upgrading the storm on Thursday.

On Wednesday night, officials said four people were killed and at least 35 were injured during the storm on Tuesday night.

The damage has left parts of the town in ruins, leveling houses, uprooting trees, and downing powerlines.

Greenfield is home to about 2,000 people. State officials have declared a disaster for the city and are applying for an expedited federal declaration.

Making matters worse, Greenfield could see further severe storms overnight, as another system is set to push through Iowa.