Investigators from the Federal Aviation Administration (search) arrived Thursday at the site of a hot air balloon crash that killed two occupants in view of horrified onlookers.

The victims plummeted hundreds of feet when they either fell out or jumped after the balloon reportedly hit at least one power line and caught fire as it ascended into the air, police said.

Bill Harwell (search), the 52-year-old who owned the balloon, and Sandi DeMoss (search), 54, were killed in the crash, Shreveport police spokeswoman Kacee Hargrave said.

FAA investigator Mary Donahue says she will be focusing on the balloon's flight path and information garnered from witnesses.

"If we have eyewitnesses, it is usually pretty straight forward," Donahue said.

She could not estimate how long it would take to reach a conclusion about the cause of the crash.

Two balloons, including Harwell's Ol' Blue, took off from Keithville's Bluebird Hill Airport just before 7 p.m. Wednesday. A few minutes later, witnesses told authorities they saw the balloon with Harwell and DeMoss aboard, then saw flames.

"I was holding my little grandbaby. And we were waving to them and talking to them," said Sharon Bivins. "They were directly overhead and were just barely over the tops of the trees. They went over and then climbed higher and higher and then dropped. And then we saw the fire and they started going up again."

Bivins said her daughter thought the flames meant they were just adding more hot air to the balloon.

"But I said 'No, it's on fire! The basket disintegrated and then a man jumped out or fell out. It was the worst thing I've ever seen in my life," she said.

Shreveport firefighters believe the basket may have struck a power line, Fire Department spokesman Brian Crawford said. A short in the 34,000-volt power line tripped breakers and caused a momentary outage in the area, AEP-SWEPCO spokesman Scott McCloud said.

Fire crews found Harwell alive but with life-threatening injuries. He was taken to LSU Hospital in Shreveport, where he was pronounced dead shortly after arrival, Crawford said. DeMoss' body was found about a block from Harwell. She had been burned and was injured when she jumped or fell from the burning craft, authorities said.

The balloon continued to drift and scatter debris before alighting at South Park Mall, which now is used as a church, authorities said.

The second balloon, piloted by Harwell's brother, Pat, was not involved in the fire or the collision with the power line and landed safely in the Cargill Park area.

Afterward, Pat Harwell talked sadly of his brother's love for flying balloons.

"I got a picture of him just before we launched. He had a grin ear-to-ear, and they were fixin' to go have a great time," he said.