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Baseball-sized hail shattered windows and tore the siding off homes in northeast Nebraska and at least three possible tornadoes hit central Oklahoma on Saturday in what forecasters warned could be a day of "life-threatening" storms in the nation's midsection. No serious injuries from Saturday were immediately reported.

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A tornado was spotted in Langley, Kan., Saturday evening, as National Weather Service tornado warnings were in effect in parts of Kansas, Nebraska and Oklahoma.

The Weather Channel reported that 40 tornadoes were reported before 7:30 p.m. EDT.

“What is now under way is potentially a very serious situation,” Bill Bunting, chief of operations for the Storm Prediction Center said. Officials warned that other areas at risk were parts of Illinois, Iowa, Missouri and Texas were at risk.

The last time the National Weather Service issued such a high-risk warning was last April, Bunting said.

Comments from the targeted region started to stream onto msnbc.com’s Facebook page Saturday evening. Their comments and their Facebook IDs:

"Oklahoma is get'n shaken up jus a bit. If they weren't ALL Around. I woulda left state! But gonna pray & ride it out here in Okie.” -- Kimberly Dawn.

“Partly cloudy and very windy in S.E. Kansas with potential for severe storms after 10 pm. You pray and keep your eyes on the weather reports.” -- Valori Richardson

“I'm east of Wichita, KS. Very muggy here. Very windy. Waiting for the storms to pop here. The local weather people are warning everyone to be prepared to take shelter even into the overnight hours. This is the real deal.” -- Diane Lowery.

Nebraska canceled its spring scrimmage football game as heavy rain, hail and lightning moved through the area an hour and a half before kickoff, The Associated Press reported. Records show the spring game has been played every year since at least 1950. In northeast Nebraska, baseball-sized hail rained down, Bunting said.

He advised the nearly 5 million residents who live in the high-risk area to listen to their NOAA weather radio, a nationwide network of radio stations that broadcast from the National Weather Service.

He expects fast-moving tornadoes to touch down after dark, a dangerous time as people may not be able to see the warning signs. The storm threat continues Sunday, he said, as storms move east through Texas, Arkansas and into the Great Lakes region and Wisconsin.

Local officials should notify residents via outdoor sirens, phone calls and social media, Bunting said.

Tornado sirens already sounded across Oklahoma City hours before dawn on Saturday. Department of Emergency Management official Michelann Ooten said one of the possible tornadoes was spotted near Piedmont, a small town near Oklahoma City where a twister killed several people last May.

Weather Service meteorologist Kevin Brown told The Associated Press that the storms Saturday morning were fairly weak but still damaged some homes.

A tornado that touched down Friday afternoon sent 10 people to the hospital with "bumps and bruises" and ripped through southwest Norman, ripping up telephone poles, shredding trees and ripping off rooftops, according to the Oklahoman. The AP reported that 100 people were staying at a Red Cross shelter that had been established.

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