ORLANDO, Fla. -- Federal investigators are focusing on why a switch failed to change positions in the monorail crash that killed an operator at Walt Disney World over the weekend.

The National Transportation Safety Board reported Wednesday that no malfunctions have been found with the automatic train stop system, nor with any mechanical parts of the switch. No mechanical problems were found with the two trains that collided Sunday.

The accident killed 21-year-old Austin Wuennenberg.

A pink train was backing up in order to change tracks from the Epcot loop to the Magic Kingdom loop shortly before the accident. However, the switch that would have allowed the pink train to be routed to the Magic Kingdom loop had not changed positions. As a result, the pink train went back down the same track it had come from and collided with a purple train controlled by Wuennenberg, according to the NTSB.

The agency said it appears Wuennenberg tried to put his train in reverse to avoid the collision.

The other train operator was not injured, but taken to a hospital because he was emotionally shaken. Five park guests were treated at the scene.

Ethan Meus, who was visiting the theme park from Dubuque, Iowa, said he and his family took the monorail to dinner at a resort hotel Saturday night. Meus, 17, watched the Magic Kingdom fireworks from the monorail on the way back to his hotel, he said, and didn't notice any problems with the train.

"It's pretty shocking to hear that a driver was killed in that accident," Meus said.

The family was planning to take the train again Sunday to visit Disney's Epcot Center, but now planned to take a bus, Meus added.

"You would think it would be so safe," said 20-year-old Lauren Shoebottom, who was visiting the park from London. "You don't expect it on holiday, do you?"

A Disney spokesperson declined to discuss details of the accident.