The next 90 minutes will be crucial to efforts to save what remains of the historic Notre Dame cathedral, French firefighters said.

“There’s a risk that the great bell falls. If the bell falls, it’s the tower that collapses. There are firefighters inside and outside,” Jean-Claude Gallet, commander general of the Paris Fire Brigade, told reporters, according to CNN.

“The next hour and a half will be crucial,” he said.

The 400 firefighters working to curb the flames may not be able to stop the blaze at all, authorities said.

“We are not sure if we will be able to stop the spreading of the flames to the northern bell tower,” Gallet said.

Deputy Interior Minister Laurent Nunez added it “is not certain” that firefighters will be able to save the 850-year-old monument.

The initial call about Monday’s catastrophic blaze notified authorities that a fire had broken out in the attic of the Gothic cathedral, Gallet said. An investigation has been opened into how the blaze started.

With Post wires