MONTREAL -- Canada's Transportation Safety Board is shedding light on how the locomotive from the Lac-Megantic disaster ended up at a United States rail yard where it nearly went to auction.

The TSB's chief operating officer says the lead engine in last summer's deadly derailment was shipped to the Maine facility after the agency tested the machine and removed key components for its investigation.

Jean Laporte says the TSB asked the Montreal, Maine and Atlantic Railway to store the locomotive on its behalf until the completion of its investigation.

On Tuesday, the TSB is set to release its final report on the disaster, which destroyed part of the Quebec town and killed 47 people.

Last month, Quebec provincial police were forced to make a sudden request to block the machine from being auctioned off because criminal proceedings were still ongoing.

The defence lawyer for engineer Thomas Harding has said his client's trial on criminal-negligence charges could have a "major issue" because what is likely an important piece of evidence in the case was allowed to leave the jurisdiction of Canadian authorities.

Tom Walsh says he also has concerns the locomotive was stored at a facility owned until recently by MMA, whose Canadian subsidiary and three of its employees -- including Harding -- are facing criminal charges for the derailment.