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(CNN) -- Former Blink-182 drummer Travis Barker and disc jockey Adam "DJ AM" Goldstein were in critical condition with extensive burns Saturday after a jet crash that killed four people, authorities said.

Federal investigators recovered the cockpit voice recorder from the crash site but said they aren't sure whether information on the device survived the blaze.

Investigators are also obtaining recordings of conversations between controllers in the tower and the jet's two-person crew, said National Transportation Safety Board spokeswoman Debbie Hersman.

"Air traffic controllers did observe sparks from the aircraft as it was going down the runway and immediately alerted fire-rescue crews at the airport," Hersman said Saturday evening in West Columbia.

Lexington County Coroner Harry O. Harman said all the dead in Friday's crash were Californians.

He identified them as pilot Sarah Lemmon, 31, of Anaheim Hills; co-pilot James Bland, 52, of Carlsbad; Chris Baker, 29, of Studio City; and Charles Still, 25, of Los Angeles.

The Associated Press reported that Baker was an assistant to Barker and Still was a security guard for the musician.

The National Transportation Safety Board has sent team to West Columbia, South Carolina, to investigate the crash.

The Learjet 60 crashed on takeoff at the Columbia Metropolitan Airport at 11:53 p.m. Friday.

Beth Frits, spokeswoman at the Joseph Still Burn Center, in Augusta, Georgia, said Barker and Goldstein arrived at the hospital early Saturday. She said both men had "extensive burns." Watch charred wreckage of the plane »

Barker and Goldstein had played at a huge free outdoor concert in Columbia's Five Points district on Saturday night, CNN affiliate WIS-TV said.

Federal Aviation Administration spokeswoman Kathleen Bergen said the twin-engine private jet was cleared for takeoff on a flight to Van Nuys, California, and began its takeoff roll a few minutes before midnight.

Air traffic controllers "saw sparks coming from the runway -- whether that was from the aircraft or its engines, we don't know," Bergen said Saturday.

"They overran the end of runway 11. They impacted the antenna array and a number of lights at the end of the runway. They went through the perimeter fence and across the roadway here," Hersman said Saturday. "There was a significant post-crash fire."

William Owens told WIS-TV he was driving down Highway 302 when he said he saw a fireball go across the road.

"I didn't know what I had seen; it was maybe 800 feet in front of me, but as I approached it closer, though, I made out a fire. By then I was able to see the tail of the jet, and I recognized it as a jet," Owens said.

Owens told the station he tried to get to the wreckage.

"It's in flames, and the fuel is running across the road, and I had to cross the fuel to get to the two guys that seemed to have been dumped on the highway," Owens said.

Owens said the two men were running around and pulling off clothing to put out the flames. He said he asked them whether anyone else was on board the plane, and they said four people were with them.

"We turned to the jet to try and see if there was anything we could do, but immediately, there was nothing anyone could do," Owens said.

The crash closed the airport, which is Columbia's main commercial and passenger terminal, and it remained closed late Saturday afternoon. The airport's Web site listed nine commercial airline flights canceled through 7 p.m. Saturday.

Hersman said the airport would not reopen until investigators finished collecting debris from the runway and crash site.

She said investigators would look at every aspect of the crash, from the pilots' schedules to the aircraft's condition. She said it was a fairly new airplane, manufactured in 2006 and certified to operate in 2007.

In addition to playing with Blink-182, Barker appeared in the MTV reality show "Meet the Barkers" along with his wife at the time, former Miss USA Shanna Moakler, according to MTV's Web site.