A new line of storms was barreling through Texas on Sunday as officials worked to assess damage from a series of tornadoes and severe weather which left at least 11 people dead overnight.

Authorities said the full extent of the damage from Saturday's spate of storms was not yet known — but warned the region should get ready for another hit. Forecasters warned of more "severe" weather and heavy rain.

Next line of storms racing east toward DFW. Major winter storm also raging in TX Panhandle & South Plains. #txwx pic.twitter.com/mITgJYFcmH — Brian James (@BrianJamesNBC5) December 27, 2015

The same storm system that spawned the deadly twisters in the Dallas area was expected to leave up to 16 inches of snow in west Texas through Sunday evening, according to the National Weather Service (NWS).

"It's going to be quite dangerous," NWS meteorologist Brendon Rubin-Oster told NBC Dallas-Fort Worth.

With west Texas on alert for snow, the areas hardest-hit overnight were waking up to assess the damage. The storms leveled homes and downed power lines. Heavy rainfall also triggered flash flooding across much of Dallas County, according to the Weather Channel.

Reports of homes having been leveled keep trickling in. Will know more in the morning. -Maj. Max Geron (@MaxDPD) December 27, 2015

The National Weather Service said early Sunday there had been 11 reports of tornadoes overnight — but stressed those numbers were not fully confirmed and said damage assessments would be carried out in the morning.

It said there was a "severe threat" in place for the Dallas Fort Worth area into the morning, adding that behind the threat would be more heavy rain.

Officials in Collin County confirmed three fatalities from the storms — including two at a Copeville gas station destroyed in the storms, according to NBC Dallas-Fort Worth. Copeville is northeast of Garland.

Eight people were killed in Garland, police there said early Sunday. The force added that 15 people had been taken to hospitals with non-life-threatening injuries and that around 600 structures had been damaged in city, about 20 miles northeast of Dallas.

Five of Garland's fatalities occurred at an intersection in the city.

Randy Gore drove up to the scene shortly after the tornado hit the intersection.

"It was terrifying," Gore told NBC Dallas-Fort Worth. "It was heartbreaking, especially being the day after Christmas."

Lamont Shrimp told the station he stopped to help peopled pinned and trapped in damaged vehicles.

"That was our main focus, helping getting them out," Shrimp said. "Getting IV's in them, just keeping them warm, talking to them, making sure there's some support."

Not far from Garland, in nearby Rowlett, officials also confirmed a tornado had touched down.

"We have several homes leveled and some areas have significant damage," Rowlett Mayor Todd Gottel said in a message to the community Saturday night urging residents to check on neighbors. "We have power lines down as well."

Dallas police said they were assisting with patrols in Rowlett to ward against looting.

.@DallasPD officers are providing assistance to Garland and Rowlett areas hit by tornados. pic.twitter.com/vMzQHv4JjR -Maj. Max Geron (@MaxDPD) December 27, 2015

South of Dallas, officials in Ellis County said around 40 homes were partially or completely destroyed by a twister which hit at around 6:01 p.m. local time.

"We have destroyed and damaged homes, please do not get out on the roads if you do not have to," Emergency Management Coordinator Stephanie Parker said on Twitter.

Footage emerged of what appeared to be a tornado near the Dallas suburb of DeSoto and there were reports of debris falling from the sky, the National Weather Service said.

The city of DeSoto said in a statement that several homes and other structures were damaged by the "tornadic activity."

Meanwhile, weather sirens sounded and flooding was reported in Dallas itself.

People run as weather sirens sound as a severe storm passes over downtown Dallas, Saturday, Dec. 26, 2015, in Dallas. LM Otero / AP

The twisters — accompanied by torrential rain, wind and some hail — were part of a weather system that could produce major flooding from north Texas through eastern Oklahoma, eastern Kansas, western Arkansas and parts of Missouri, according to The Associated Press.

The tornado activity comes days after tornadoes and severe storms swept through parts of Mississippi, Tennessee, Arkansas and Alabama, killing at least 18 people.