Charlotte, N.C. ? A commuter plane taking off in clear weather Wednesday veered sharply back toward the airport, hit a hangar and crashed in flames, killing all 21 people aboard.

The cause of the nation’s first deadly airline accident in more than a year was not immediately clear. Aviation officials said the pilot reported an unspecified emergency to the tower just before the crash.

US Airways Express Flight 5481 hit the corner of the hangar at full throttle moments after leaving Charlotte-Douglas International Airport for Greer, S.C., officials said. No one on the ground was injured.

Dee Addison, who works at an airport business 500 yards away, ran outside after hearing a boom.

“It was like a frenzy. People were running out of the (hangar),” she said. “At the time we didn’t know a plane had actually crashed. It didn’t even look like a plane. It was totally demolished.”

Heavy smoke poured from the wreckage for hours, so thick “you could taste it in your mouth,” Addison said. The US Airways hangar was scorched and battered.

The Beech 1900 twin-engine turboprop was carrying 19 passengers and two crew members. It took off to the south, then cut back toward the airport, airport director Jerry Orr said.

The pilot, Capt. Katie Leslie, contacted the tower to report an emergency, said Greg Martin, a Federal Aviation Administration spokesman. But the transmission was cut short and the emergency wasn’t identified, he said.

Emergency personnel work the scene near the charred US Airways hangar after a commuter plane crashed into it at Charlotte/Douglas International Airport in Charlotte, N.C. Wednesday's crash killed 21 people, authorities said.

The flight data recorder and cockpit voice recorder were recovered and are being analyzed, said John Goglia, a National Transportation Safety Board member.

“Both were burned, but it does appear they were in decent shape,” Goglia said.

The FBI said there were no immediate indications of terrorism.

Goglia said investigators, though, will consider every possible cause, and will review the pilot performance, maintenance records, the plane’s structure and the flight’s passengers and freight.

“At this point, nothing is out of the question,” he said.

Goglia also said bolts and small pieces of debris were found on the runway after the crash, but the NTSB hasn’t determined if they came from the crashed plane.

The plane, built in 1996, was operated by Mesa Air Lines under the US Airways Express name. It had flown 15,000 hours and performed 21,000 takeoffs and landings.

FAA records show the aircraft was involved in five in-flight incidents that the NTSB said could affect safe operations. In one incident, the right engine lost oil pressure in November 2000 and the crew had to shut it down. The plane landed safely and the engine was replaced.

There have been eight fatal accidents involving Beech 1900s in 40 years, according to NTSB records. The most recent was Dec. 9 when a private flight crashed in Eagleton, Ark., killing three people.

The Charlotte crash came after a year in which there were no deaths aboard a passenger or cargo airliner in the United States. The last fatal crash was that of an American Airlines jetliner in New York City on Nov. 12, 2001, in which 265 people died.