Four people were killed and hundreds injured after an Amtrak train carrying nearly 500 passengers derailed in northern Florida Thursday evening.

It could not be immediately determined why the Auto Train derailed, knocking down pine trees lining the tracks, officials said. The track had been inspected hours before the crash and had been in good condition.

Florida Highway Patrol spokesman Bill Leeper said that those killed were among 468 passengers and crew on board the Auto Train, which travels between Sanford, Fla., and Lorton, Va. He said about half of the survivors were injured. He didn't know how many were seriously hurt.

The train, billed by Amtrak as the longest passenger train in the world, is a favorite among families traveling between the Mid-Atlantic and Northeast and Orlando's theme parks. It crashed along U.S. Highway 17, about 60 miles north of Orlando, in an area known as the "Fern Capital of the United States."

Amtrak said the train carried 440 passengers and 28 crew members.

Putnam County sheriff's Capt. Keith Riddick said that 14 passenger cars derailed.

He said investigators have not found any cars or vehicles on the track that could have caused the wreck.

"Suddenly you could feel the brakes scraping," said David Sheldon, 71, who was traveling with his wife, Sylvia, from Boca Raton.

Sheldon said it took about 30 seconds for the train to come to stop.

"It seemed like forever," he said.

"We just started hurtling and left the track and the next thing we knew, we were bouncing off the walls," said Bernie Morgan, traveling from Naples to Doylestown, Pa.

Rescue officials, using ladders to reach the overturned cars, helped survivors out of the train and reached through the windows to get to the people still trapped inside. Medics and fellow passengers were seen helping the injured.

In the makeshift triage center, rescue workers aided victims, applied first aid and passed out cups of water to those who were unscathed.

Robert Dodd Sr., 74, of Willingboro, N.J., was standing in the middle of the triage unit as his wife Betty laid on a backboard with a white brace around her neck and a round cut on her right elbow.

He said he and his wife were sitting down to dinner when the train derailed.

"The girl said, 'Do you want white or red wine?'" Dodd said. "At first I said, 'White, no give me red' and that's the last thing I remember."

Wearing a priest's collar and black baseball cap, the Rev. Lamar Taylor, the Volusia County sheriff's chaplain, walked from stretcher to stretcher, backboard to backboard, putting his hand on shoulders and comforting victims.

"They're mostly in the state of mental shock," Taylor said. "This is as bad as I've seen."

Three passengers were flown by helicopter to Shands Hospital at the University of Florida in Gainesville, Dr. Kevin Ferguson said. One person was in critical condition with potentially life-threatening injuries, while the other two were in serious condition, he said.

Ferguson would not release the names of the passengers.

Nine trauma patients — five males, four females between 40 and 80 years old — were airlifted to Halifax Medical Center in Daytona Beach, said Kate Holcomb, a hospital spokeswoman. They are in serious condition, she said.

A bus carrying 26 people with minor injuries were being examined at Memorial Hospital-Peninsula in Ormond Beach, spokeswoman Desiree Paradis said.

In Washington, the NTSB said a team of investigators was headed to the crash site.

The train derailed shortly after 5 p.m., according to Amtrak. The train consisted of two engines, 16 passenger cars and 202 automobiles stacked in 23 specially designed cars. The tracks are owned, operated and maintained by CSX Corp.

CSX spokeswoman Jane Covington said that a veteran company inspector visually examined the tracks about eight hours before the crash and that they had been in good condition.

"He knew that section of track like the back of his hand," Covington said.

CSX officials were investigating the accident, awaiting the NTSB team, she said.

The tracks are part of a CSX line normally used by 28 trains in a 24-hour period. Another Amtrak train and five to seven freight trains were rerouted late Thursday to avoid the area, Covington said.

The area around the derailed cars was cordoned off with yellow tape as rescue workers from throughout the region arrived to help. Television helicopter shots showed cars on their sides scattered along the tracks. Firefighters, carrying backboards, were climbing through windows to get inside the cars.

Rescuers were going car to car, painting orange C's on the bottom of the overturned cars once they determined the car was cleared of people.

Ambulances and emergency vehicles crowded a road nearby, and school buses were being used to take passengers away from the scene.

Early Friday, about 21 of the train's 28 crew members arrived at a hotel near Universal Studios in Orlando. They will stay there until later in the day as they decide how to return to the Washington, D.C., area, said Julie Byrne, crew chief of the crashed train.

The American Red Cross sent disaster response teams to the crash site and to Lorton. The teams include mental health workers to comfort victims, family members and emergency workers.

Emergency response vehicles were also sent to the derailment site to distribute meals and information to victims. The American Red Cross was also prepared to set up a shelter there if needed, said Carol Miller, the organization's spokeswoman in Washington.

In 1998, Auto Train hit an empty car on tracks at a crossing in Jarratt, a rural town in southern Virginia. The train, traveling 65 mph, remained upright when the front wheels of the lead engine derailed. There were no injuries.

The Associated Press contributed to this report.