The US National Weather Service said there were reports of ten tornadoes hitting the area on Wednesday, flattening buildings and uprooting trees across at least four counties near the Dallas-Fort Worth area.
Hardest hit was Granbury, a town of 8,000 people about 35 miles south-west of Dallas-Fort Worth.
In Hood County, where Granbury is located, spokesman Tye Bell said six people were dead, seven missing and at least 45 injured.
All six of the people confirmed killed were found in Rancho Brazos, a neighbourhood of around 110 mostly single family homes on the fringe of Granbury that bore the brunt of the winds, Hood County Sheriff Roger Deeds said.
The area includes 61 Habitat for Humanity homes, the charity organisation said on its website. Habitat for Humanity, well-known because former US President Jimmy Carter has long been a supporter, uses volunteers to build and repair homes for residents on low incomes.
Frank Gamez, a builder who works in Granbury, said he found a friend dead on Wednesday night as he and other people searched the neighbourhood.
Mr Gamez said: “We lost one of our friends. We found him laying on the ground.”
Mr Gamez said one home, which was to be officially presented to a low-income family this weekend, was destroyed.
He said: “There’s nothing there but concrete slabs.”
Preliminary reports showed that the US National Weather Service issued a tornado warning for Granbury 26 minutes before the twister struck, according to Mark Wiley, emergency response meteorologist at the agency’s Forth Worth office.
This is an unusually long lead time as the average warning time is between ten and 12 minutes, he said.