Police in Canada have opened a criminal investigation into Sunday's fatal fuel train blast in the town of Lac-Megantic.
Dozens of buildings were destroyed when the runaway train crashed off the tracks into the town centre.
Quebec Police Inspector Michel Forget told reporters police have discovered "elements" that have led to the opening of a criminal inquiry.
Mr Forget gave few details of the investigation and said it is unclear whether it will lead to criminal charges being filed, Reuters reports.
Police have raised the death toll to 15, saying the total number of dead and missing is 50.
Many of those missing are thought to have been drinking at a popular downtown bar when the explosions occurred.
The company that operates the train speculated on Tuesday that the train's airbrakes may have been switched off when a small fire was put out earlier in the evening.
Police say the blast is unlikely to have been caused by terrorism.