Severe storms and tornadoes struck Oklahoma early Sunday, causing damage across the state, including overturned cars, damaged buildings, and power outages affecting tens of thousands of homes and businesses. Officials reported that at least 11 people required hospitalization due to injuries.

The damage was most severe in and around Oklahoma City, the state capital, but reports of damage came from various locations across the state. Early morning storms triggered tornado warnings that extended south to the Arkansas border. Heavy rains led to flash flooding in certain areas, and one lightning-related house fire was reported.

Over 99,000 Oklahoma homes and businesses lost power during the overnight storms. By midday, this number decreased to under 34,000. As of midday, no fatalities had been reported.

Richard Thompson, the forecast chief for the National Weather Service Storm Prediction Center in Oklahoma, believes six or more tornadoes hit the state overnight. Forecasters are warning Oklahoma residents to prepare for more heavy rain and potential severe weather through Monday.

“We’re not done with it yet,” Thompson said.

In Choctaw, a town east of Oklahoma City, firefighters and police officers conducted door-to-door checks Sunday morning to assess injuries.

“It leveled a complete neighborhood in Choctaw,” Chad Allcox, the town’s mayor, told The Associated Press. He added that debris was hindering search and rescue efforts. “Power lines are down everywhere … a lot of the roads are blocked, hard to get through. Very large trees blocking roadways.”

Scott Douglas, a spokesman for the Oklahoma City Fire Department, told the AP that heavy rain and the continuing threat of tornadoes in the early morning darkness complicated early search and rescue efforts, describing a first sweep of hard-hit areas around 1:30 a.m.

“It was a heavy downpour. We were trying to sweep the area with another possibility of a tornado coming through,” he said. “So that was in the back of our minds, too.”

Emergency workers had to free two people from an overturned mobile home, including a woman injured when an air conditioner fell on her leg, Douglas said.

The extent of the damage became clearer as daylight arrived. Local television footage showed downed power lines, damaged homes, overturned vehicles, and debris-filled neighborhood streets.

Douglas said 11 people were taken to hospitals with injuries that were not life-threatening. “There were some other minor injuries, some walking wounded, that were going to get treatment on their own,” Douglas said.

Allcox said early weather warnings and tornado sirens likely saved lives.

A number of shelters, including one opened at a casino by the American Red Cross, are available for displaced residents or those without power, the Oklahoma Department of Emergency Management said.

The Oklahoma Heart Hospital South also sustained damage, state health officials said.

At the University of Oklahoma, school officials had urged students and staff to seek shelter and move to the lowest floor as the storms approached campus after midnight. The National Weather Service office in Norman also issued urgent warnings, posting on social media that “If you’re in the path of this storm, take cover immediately!”

Parts of Oklahoma remained at risk for more heavy rainfall and thunderstorms later Sunday.