Torrential rain caused flooding Thursday in the Houston area, with officials ordering some residents along a river to leave and telling others they may wind up stranded.

"This is a life-threatening situation,” the county's top elected official, Harris County Judge Lina Hidalgo, said.

Of particular concern is an area along the San Jacinto River, which was expected to keep rising as more rain falls and officials release extra water from an already full reservoir. Officials ordered people in an area along the river in northern Harris County, where Houston is located, to evacuate.

“We want you out of this area,” Hidalgo said at a news conference Thursday afternoon. She did not say exactly how many people were ordered to evacuate.

Officials asked that residents farther south along the river leave or prepare to be stranded by rising water for two to three days, Harris said.

Hidalgo said the San Jacinto River is normally 45-50 feet (13.72-15.24 meters) above sea level, but is expected to reach 78 feet (23.77 meters).

The county opened three shelters for displaced residents, with a fourth planned.

In Montgomery County, just north of Harris County, officials issued a voluntary evacuation order and said roads were closed because of flooding along the river.

The area got about 5 to 8 inches (13 to 20 centimeters) of rain within 24 hours, with some spots getting as much as 10 to 12 inches (25-30 centimeters) of rain, said National Weather Service meteorologist Hayley Adams. More rain was expected through Friday morning.

The storm brought down trees and left vehicles stranded. It prompted the San Jacinto River Authority to close Lake Conroe and increase water releases from the dam that created the reservoir.

Nine people were rescued from rising water, the Houston mayor's office said. No injuries or deaths had been reported.

Dawn O’Leary, a resident of Cleveland, about 45 miles (72.42 kilometers) northeast of Houston, was caught off guard by the rising floodwaters. “I was trying to get to work,” she said, but the roads were so bad that she could not make it.

Emergency management officials said the area could see flooding similar to that caused by the remnants of Tropical Storm Imelda, which dumped more than 40 inches (102 centimeters) in some locations in 2019.