A police investigation into a fiery car crash that killed two people at the border of Niagara Falls has been closed.

Officials say the black box that retained the car’s telematics data was destroyed in the crash, leaving the cause of the crash a mystery.

Because of its destruction, police officers on the American side of the border were unable to determine whether or not the crash was due to a mechanical fault or driver error.

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According to Robert Restaino, the mayor of Niagara Falls, NY, the investigation can be reopened if new evidence is discovered.

Last year, following the crash’s immediate aftermath, speculation and fears that it may have been an act of terrorism quickly began to circulate — however, the FBI’s Buffalo office said it found no signs indicating such and passed the case over to local authorities.