Watch the US National Transportation Safety Board detail its report into the Ohio train derailment.
This video shows the team discussing their preliminary findings that were released on the morning of Thursday, 23 February.
The initial details confirm an earlier theory that a wheel-bearing overheated and broke just before the accident.
It also outlined that a defect detector installed along the tracks picked up on the failing bearing.
They also reported that the train had been travelling at 47 mph before the accident - slightly less than the 50 mph speed limit for locomotives.
Residents were evacuated after the derailment on 3 February and locals were concerned about potential contamination of air and water following a controlled burn of toxic chemicals aimed at preventing an explosion.
The EPA found that lab samples of local water had not been contaminated.
Click here to sign up for our newsletters.
