(CNN) -- Multiple tornadoes pummeled a region in northeast Nebraska Monday, killing one and causing damage that was still being assessed as the sun went down.
And the severe weather is not letting up. A tornado watch remains in place until early Tuesday morning.
One city, Pilger, has been closed to all but emergency personnel, the state's emergency management agency said Monday night. Severe weather in the area caused damage in at least four towns -- Pilger, Wisner, Stanton and Pender, according to the governor's office.
At least 15 patients were transported to Faith Regional Health Services for treatment, and "many more" were expected to arrive, hospital spokeswoman Jacque Genovese said.
Officials were assessing the damage, trying to determine how many are injured and how much damage has been done.
"We're still digging people out," said Sanford Goshorn, the emergency manager in Stanton County, where Pilger and Stanton are located.
Wisner is in Cuming County, and Pender in Thurston County.
In the immediate aftermath of the tornadoes, it was unclear how many touched down in this corner of Nebraska. But at least two major tornadoes touched down at the same time, CNN Meteorologist Chad Myers said.
The two tornadoes -- side by side and straddling a road -- were a menacing sight.
The state emergency management agency reported "severe damage" across the affected counties.
"We are still in a response mode in these communities," emergency management operations officer Earl Imler said. "We are collecting damage reports from local officials on the ground."
Nebraska Gov. Dave Heineman issued a state of emergency, putting the National Guard on standby.
According to the governor's office, the reported fatality happened when a tornado picked up a car and dropped it.
The National Weather Service also issued a tornado emergency warning for the town of Burwell, located in Garfield County, where a confirmed "large, violent and extremely dangerous tornado" was sighted. The storm included hail and residents in its path were urged to take immediate cover.
Damage from the storm also reached the area of the Nebraska-Iowa border.
"We've had reports of brief touchdowns as the storms near Sioux City, Iowa," said National Weather Service Meteorologist Todd Heitkamp said. "We've had widespread wind and flooding damage due to the series of storms that have been ongoing today. We've had reports of up to 4 inches of rain within an hour in the tri-state area (South Dakota, Minnesota, Iowa). The main thing is widespread tree damage."