Notre-Dame investigators say no evidence thus far fire was a criminal act
But Paris's prosecutor says negligence has not been ruled out as a factor
The Paris prosecutor's office says there is no evidence from a preliminary investigation to suggest that a fire that destroyed large parts of Notre-Dame Cathedral was criminal.
The prosecutor's office said in a statement on Wednesday there are several hypotheses about the cause of the April 15 blaze, include a malfunctioning electrical system or a smouldering cigarette.
It also announced the opening of a new investigation for "involuntary degradation by fire through manifestly deliberate violation" of security rules or simple imprudence.
Three judges will head the probe.
The fire tore through the roof of the 13th-century cathedral, destroying the spire, which toppled in flames, and sections of the interior. It has left the crippled monument, once a major tourist attraction, barricaded to the public.