ORLANDO (AP) – The National Transportation Safety Board is joining the list of agencies investigating the death of a 21-year-old train operator during a monorail accident at Walt Disney World last weekend.

NTSB spokesman Peter Knudson said Tuesday that it is the first time the agency is investigating an accident involving a private transportation system on private property.

He says the agency is getting involved since the monorail system carries large numbers of passengers.

Austin Wuennenberg died of multiple traumatic injuries after one monorail train crashed into another last Sunday.

The accident also is being investigated by the Occupational Safety and Health Administration and the Orange County Sheriff’s Office.