There is no evidence that the Notre-Dame fire was the result of criminal action, the Paris prosecutor has said.
A two-month preliminary investigation into the cause of the nine-hour fire which wrecked the iconic Paris landmark found that it most likely started accidentally.
However, an investigation has been opened into the possibility of negligence by one or more parties regarding the huge blaze, thought to have been caused by an electrical fault or a cigarette.
"If certain failings, which may explain the scale of the fire, have been brought to light, the investigations carried out to this date have not yet been able to determine the causes of the fire," said a statement from Paris prosecutor Remy Heitz.
"For now, there are no indications of a criminal origin," he added.
The fire ripped through the 13th century cathedral - one of the most famous buildings in the world - on the evening of 15 April as the world watched in horror, destroying the roof as well as the building's spire.
Firefighters managed to save the main bell towers and outer walls from collapse before bringing the fire under control.
The prosecutor's office said in a statement on Wednesday that several hypotheses about the cause of the fire include a malfunctioning electrical system or 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.