MONTREAL -- Quebec police investigating the Lac-Megantic train disaster say they've visited the United States four times to seize documents and to interview witnesses -- including railway chairman Ed Burkhardt.
A provincial police spokesman says investigators working the case also have plans return to the U.S. to gather more evidence.
Lt. Michel Brunet says the cross-border investigation was conducted through Interpol and at least part of it took place at Burkhardt's Chicago-area office.
Earlier this week, Canada's Transportation Safety Board released its final report into the deadly derailment -- a document that criticized Burkhardt's railway for its role in the disaster and for its weak safety culture.
The now-bankrupt Montreal, Maine and Atlantic Railway and three of its employees have each been charged with 47 counts of criminal negligence causing death -- one for each victim of the catastrophe in July 2013.
Brunet says the case is still open and Quebec prosecutors could still lay more criminal charges.
He says officers questioned Burkhardt, who was chair of the former MMA, as well as other highly placed officials with the railway.
