At least seven people were killed Sunday in south Texas and several others were injured when a car plowed through a group waiting at a bus stop outside a migrant aid center, police said.

Law enforcement said they were treating the incident as an accident for now, though a witness told AFP the driver had yelled insults at the group before accelerating.

The gray sport utility vehicle "went through a red light and ran over several people" at around 8:30 am in Brownsville, a border city at the southernmost tip of the state, local police spokesman Martin Sandoval told AFP.

He said seven people died and "nearly 10" other people were injured.

Witness Luis Herrera, whose arm was hurt in the incident, told AFP the crash was "sudden."

"A woman went by in a car and warned us to get out of the way," he said.

"It was a matter of moments. The killer came (through) in the car, gesturing at us, insulting us," the 36-year-old Venezuelan said.

Herrera then described the driver as accelerating the car to full force.

The motorist, whom Sandoval said was also taken to the hospital, was detained by witnesses until police arrived. He has been charged for now with reckless driving.

"More than likely there's going to be other charges coming on later," Sandoval earlier told a local ABC affiliate, without clarifying what the additional charges might be.

Authorities have launched an investigation into whether the fatal crash was an accident or intentional, Sandoval said.

"We're looking (into it)," he told AFP.