A tornado killed two people as it tore through the northern Louisiana city of Ruston early Thursday, sending trees into houses, ripping roofs off buildings and causing a local public university to cancel classes, officials said.

"Devastation is the way it looks," said Ruston Mayor Ronny Walker after flying over the city in a helicopter to assess the damage. "The number of houses with trees completely through them was incredible."

The tornado was part of a thunderstorm that left a trail of damage from eastern Texas into northern Louisiana but Ruston — a city of about 24,000 people — appeared to get the worst of it.

A mother and son were killed when a tree fell on their home in Ruston overnight, officials said. During a news conference, Gov. John Bel Edwards identified the victims as Kendra Butler, 35, and Remington Butler, 14, who was a high school freshman.

Edwards declared a state of emergency as he toured the region and met with officials. Edwards, who's led the state through multiple natural disasters, said the damage he saw Thursday was remarkable in the way it spared and devastated areas so close together.

"You see one side of the street seems perfectly normal and everything on the other side of the street severely damaged," he said.

Walker said that immediately after the tornado swept through Ruston, about three-quarters of the area was without power. Restoration was ongoing, but he said by the end of the day they expect about 25% to 30% of the town will be without power.

The tornado was part of a severe weather system that pounded Texas with rain Wednesday, killing a woman and two children caught in a flash flood, before moving into Mississippi on Thursday.

National Weather Service hydrologist C. S. Ross said the tornado hit Ruston at 1:50 a.m. It was part of a line of "continuous damage" that stretched about 150 miles from Texas into Louisiana, he said. Officials would be using satellite data to determine whether it was a single tornado that ripped through the entire area, although Ross said that does not appear likely.

The National Weather Service said on Twitter that the tornado that hit Ruston was an EF3, meaning it had winds of at least 136 mph. They said an EF1 tornado hit near Mooringsport, La., while an EF2 tornado hit near San Augustine, Texas.

In central Texas, the National Weather Service classified a tornado that smashed a Bryan-area warehouse on Wednesday afternoon as an EF2 with winds estimated at up to 120 mph.

At Louisiana Tech University, classes were canceled Thursday and Friday, the university said. The university said no students were reported injured, but trees and power lines were down in several places on campus.

The university's sports facilities got hit the hardest, officials said.

"Our softball and our soccer facilities are completely demolished. Our baseball facility is severely damaged," said Malcolm Butler, the university's associate athletics director.