WATCH: Onlookers kneel, sing 'Ave Maria' as they watch the Notre Dame Cathedral burn

As the iconic and historic Notre Dame Cathedral burned into Monday night, Parisians and tourists helplessly watching the inferno knelt and sang "Ave Maria," the famous Catholic prayer to the Virgin Mary.

Their chorus created a hauntingly sad and beautiful backdrop to the scene they were witnessing; a centuries-old Christian landmark slowly being destroyed by flames despite the efforts of hundreds of firefighters to control it.

What's going on?

Notre Dame Cathedral caught fire Monday afternoon, presumably due to an accident related to renovations that were being made to the landmark.

The roof and spire of the cathedral collapsed, and officials initially believed that the entire structure would burn to the ground. However, as of Monday evening, fire officials said that the building would be partially saved.

"We now believe that the two towers of Notre Dame have been saved," Paris fire chief Jean-Claude Gallet told Reuters. "We now consider that the main structure of Notre Dame has been saved and preserved

Officials also said that at least some of the most precious art contained within the cathedral had been saved, although it will be some time before the total scope of the damage and loss is known for sure.

One fireman has been reported as seriously injured while fighting the fire. As many as 400 firefighters were working to control the fire throughout the day.

French President Emmanuel Macron is already looking ahead to efforts to rebuild the cathedral.

"I'm telling you all tonight—we will rebuild this cathedral together," Macron said, according to CBS News. "This is probably part of the French destiny. And we will do it in the next years. Starting tomorrow, a national donation scheme will be started that will extend beyond our borders."

About Notre Dame Cathedral

The building of Notre Dame cathedral began in 1163, during the reign of King Louis VII, and was completed in 1345. It has become a rich symbol of French and Catholic history over the centuries, as well as a tourist attraction that draws millions of tourists each year.