SIOUX FALLS, S.D. — Emergency officials in Sioux Falls are surveying significant damage and developing a response plan following a confirmed EF2 tornado touched down just before midnight Tuesday. 

Meteorologist Todd Heitkamp confirmed the touchdown during a news conference Wednesday morning, saying one area he surveyed was hit by a tornado packing winds of approximately 125 miles per hour. He says the confirmation is based on debris patterns and how far debris was blown. There may be additional sites where the tornado touched down. 

Heitkamp estimates three-quarters of South Dakota's largest city was impacted by the fast-moving storm system that tore through, including straight line winds in excess of 90 and 100 miles per hour. 

Fire Chief Brad Goodroad says at least 37 structures in the city either collapsed or have structural issues. There are some reports of injuries, but no word on any fatalities.

Sioux Falls Public Works Director Mark Cotter is compiling a list off damage across the community. He says tree damage is significant, with streets blocked, power lines down and traffic signals not working. Xcel Energy has called in repair crews, and a spokesperson says 400 people will soon be on the ground attempting to restore power.  

The National Weather Service has determined that three EF-2 tornadoes struck the city overnight, lead meteorologist Todd Heitkamp said Wednesday.

Xcel Energy says as many as 25,000 customers were without power at one point because of the damage, but that number dropped about 2,100 customers by 6:30 a.m.

The Red Cross opened a shelter at the Sioux Empire Fairgrounds' armory for people displaced by the storm.

Sioux Falls, with an estimated population of 187,200, is about 240 miles southwest of Minneapolis.

Sioux Falls Public Schools delayed classes Wednesday as crews worked to clear debris, and city officials in Sioux Falls urged people to stay off the streets until 8 a.m.

Mayor Paul TenHaken said the city was looking into a "breach of protocol" with its outdoor siren warning system. TenHaken said most of the sirens sounded in the southwest part of the city, where the most serious damage occurred, but the system is supposed to sound sirens citywide.

Among the buildings damaged was Avera Behavioral Health. The storm ripped off part of the hospital's roof and caused significant damage to the building's windows, according to Avera spokeswoman Michelle Pellman.

"Seven Behavioral Health patients have been transferred to the Avera Heart Hospital," Pellman said. "Only one patient suffered an injury and it was non-life threatening."

The Avera Heart Hospital also had damage to its lobby and windows, but all patients are safe, Pellman told the Argus Leader. She said people should stay away from the area because of flooding and debris concerns.

Other damaged businesses included an Advanced Auto Parts store where a wall collapsed. Kohl's and Best Buy lost part of their roofs and Pizza Ranch suffered heavy damage.

The trouble may not be over: National Weather Service forecasters warned of possible severe thunderstorms Wednesday across the Plains and Upper Midwest, stretching from western Nebraska, Minnesota and Iowa to Wisconsin. The likeliest threat was in western Nebraska, and the weather service warned of possible flash flooding in the north-central part of the state.