A news conference by the National Transportation Safety Board Sunday evening was light on details, leaving unanswered the most pressing questions from the crash.

The investigative agency declined to answer questions about what the work crew was doing, how a maintenance vehicle ended up on an active track and why the train's operators were not made aware the maintenance crew was there. These would all be questions explored by their investigation, which they said would look at mechanical, operations, track, human performance, scheduling and survival factors.

Recovered from the train were the event data recorder, which keeps information about the train's status and speed, and the inward and forward facing cameras.

Investigators said the data will be analyzed at laboratories in Washington D.C.