The monorail accident that killed a Walt Disney World train operator may have been triggered by another worker who mistakenly radioed others that he had activated a track switch.

The Orlando Sentinel reported Thursday that the employee has told investigators he thought he had activated the switch before radioing that it had been done. But the switch never moved from the main line to the spur, and investigators have found no evidence of a mechanical malfunction.

Two trains on the monorail collided over Fourth of July weekend, killing college student Austin Wuennenberg, who was operating one of the trains.