A row of houses are left flattened by a tornado in this aerial photograph taken over Granbury, Texas on May 16, 2013. [Photo/Agencies]

GRANBURY, Texas - At least six people were killed when a powerful tornado ripped through a neighborhood including a Habitat for Humanity low income housing area in the north Texas town of Granbury on Wednesday, marking the deadliest severe storm outbreak in the United States this year.

Authorities warned the death toll could rise because seven people were missing after the storms, which struck from early evening to around dusk, flattening buildings and uprooting trees across at least four counties near the Dallas-Fort Worth area.

The National Weather Service said there were reports of 10 tornadoes touching down in the area.

Hardest hit was Granbury, a town of 8,000 people about 35 miles (56 km) southwest 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, most from a single subdivision of homes in the town.

Frank Gamez, who works in construction in Granbury, said he found a friend dead on Wednesday night as he and other people were searching the neighborhood.

"We lost one of our friends. We found him laying on the ground," Gamez said.

Hood County Sheriff Roger Deeds said authorities were searching homes to try to find people who might still be trapped in the rubble.

All six of the people confirmed killed were found in Rancho Brazos, a neighborhood of around 110 mostly single family homes on the fringe of Granbury that bore the brunt of the winds, Deeds said.

The area includes 61 Habitat for Humanity homes, the charity organization 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 low income residents.

Gamez said one Habitat for Humanity home that was to be officially presented to a low income family this weekend, was completely destroyed.

"There's nothing there but concrete slabs," he said.

Video of the area showed homes flattened, power lines down and roads blocked by debris in the area. Bulldozers were clearing roads so people could be moved out of their houses.

Other counties hit by the wave of storms were Johnson, Montague and Parker, according to Corey Mead, forecaster at the National Weather Service Storm Prediction Center in Norman, Oklahoma.

In Parker County, about 14 homes and farms had severe roof damage and other structural damage and a few buildings were destroyed, said Parker County Judge Mark Riley. No injuries or deaths were reported.

A nurse at Bowie Memorial Hospital in Montague county, Texas said a tornado hit the local country club. There were no injuries or deaths reported in Montague county.

The winds were so strong in Johnson county that a large trailer was blown into a home and rested on a car in the town of Cleburne, Texas.