Utility crews were working Thursday to restore electricity to thousands of customers knocked off the power grid when thunderstorms swept through Arkansas.

Hail and high winds generated by severe thunderstorms Wednesday also damaged roofs and structures across the state.

Storms knocked out power in much of Pine Bluff and the surrounding area, as well as in the Malvern-Arkadelphia area. Most customers had their electricity back by Wednesday night, but an Entergy Arkansas spokesman said others would not get power restored until late Thursday.

A funnel cloud was spotted in Dallas County, but no touchdown was confirmed, and Fordyce reported gusts of 72 mph, said Joe Goudsward, a meteorologist with the National Weather Service in North Little Rock.

Wednesday morning, about 600 students were evacuated from Robinson Junior High School in Pulaski County after a tree fell near tanks holding diesel fuel. Pulaski County Sheriff's Department spokesman John Rehrauer said the junior high was evacuated for about three hours and that the tree was safely removed from the area.

In Malvern, a prison guard was hospitalized after lightning struck a 20-foot-tall tower. The guard suffered burns to her face and chest.

The storm also knocked down the right-field wall at Taylor Field in Pine Bluff.

The National Weather Service said trees were blown down in places from southwest Arkansas to as far north as Mountain Home. A FedEx Corp. truck was blown into the median of Interstate 530 near Redfield and three-quarter-inch hail fell at Batesville and Dardanelle.

A train derailed at Wabbaseka east of Pine Bluff, the National Weather Service said. Jefferson County officials said two mobile homes were badly damaged.

"It's pretty widespread," Goudsward said. "We've got wind damage in Clark County, Benton County, Bradley County and Jefferson County. It was pretty much statewide. The only place that really escaped was the north."

Entergy Arkansas spokesman James Thompson said that as of Thursday morning, 7,900 customers were without electricity because of the storms, down from a peak of 26,000 outages early Wednesday.

Thompson said the Malvern-Arkadelphia-Gurdon area had the highest number of remaining outages, with 3,100 customers still without electricity, while 2,400 customers were without power in the Pine Bluff area and outages in the Stuttgart area totaled 1,500. The remaining customers without power were scattered around the state, he said.

Thompson said the outages were caused by high winds that brought down trees, snapped poles or caused lines to flap into each other. He said some transformers were struck by lightning. Crews from Texas and Louisiana were en route to help restore electricity, Thompson said.