Paris public prosecutor Remy Heitz said on Tuesday that there is no sign the fire was started on purpose, with an accident remaining the most likely cause of the Notre Dame Cathedral fire.
"We are favouring the theory of an accident," Heitz told reporters, adding that 50 people were working on a "long" and "complex" probe into what caused the fire.
Remy Heitz assured that all means would be used to ascertain the origin of the fire and confirmed that witness hearings are still in progress.
Paris investigators have questioned the workers who were engaged in the restoration of the Notre Dame cathedral, which was ravaged by fire on Monday, BFMTV broadcaster reported on Tuesday, citing the prosecutor's office.
According to broadcaster, investigators have identified the workers who carried out the restoration works, in particular, to rebuild the cathedral's destroyed spire and questioned them. The interrogations are expected to continue throughout the day, the news outlet added.
A fire broke out at the Notre Dame Cathedral on Monday, resulting in the collapse of the cathedral's spire and the destruction of its roof. French President Emmanuel Macron described the incident as a "terrible tragedy" and promised to rebuild the 856-year-old cathedral.