Russ Gober, lead investigator for the National Transportation Safety Board, said the engineer of the southbound Silver Palm radioed, "I made a bad mistake. I made a bad judgment." The engineer's name was not released.
The southbound train was traveling at 55 mph when it slammed into the northbound train, which was moving into a siding at 14 mph, Gober said. The southbound train was supposed to have stopped while the other train moved to the siding.
One train was headed to Miami from New York City, while the other was on its way to New York City from Miami. The trains, both called the Silver Palm, were carrying a combined 300 passengers when they collided on the west side of downtown Jacksonville at about 3 a.m.
Four locomotives and seven cars derailed, said Jane Covington, a spokeswoman for CSX Transportation, which owns the track.
Modesto Romero, his wife, Maria, and their children, Nelida, 11, and David, 14, were asleep in a cabin when the collision sent Mrs. Romero tumbling to the floor.
"I was asleep and then I heard my wife. I jumped up and held up the top bunk where my kids were sleeping," said Romero, who was traveling to Miami from Newark, N.J., to visit relatives. "They were a little scared."
Passenger Rhodell Green of Hollywood, Fla., said the accident jolted her out of her seat.
"I didn't know what happened. It felt like just a big hit," she said. "I thought we had run over a truck or something."
Five of seven the injured were taken to St. Vincent's Medical Center, where they were treated for cuts and bruises.
Three others were sent to Methodist Medical Center. Two were treated and released and another was being held for observation in the emergency room, said hospital spokeswoman Joy Batteh-Freiha.
Passengers traveling south were to be put on another train and northbound passengers were put on buses.