PARIS, April 21 (Xinhua) -- Some 180,000 bees in three hives installed on the rooftop of the Notre Dame Cathedral have miraculously survived Monday's infernal fire that destroyed most of the cathedral's roof and toppled its landmark spire.

Nicolas Geant, the cathedral's beekeeper, has confirmed that the bees are alive and buzzing. "It's a big day. I am so relieved. I saw satellite photos that showed the three hives didn't burn," Geant told Associated Press.

The beekeeper had feared for the fate of the bees as fire engulfed much of the cathedral's roof on Monday evening. Excessive heat is fatal for bees. When European bees sense fire, they would stay inside the hive and protect their queen. If the wax that protects their hive melts, the bees simply die inside, Geant explained.

The hives sit on top of the southern part of the cathedral, around 30 meters below the main roof. As a result, they remained untouched by the flames.

Smoke may also have played a role in saving the bees. Carbon dioxide makes bees drunk, puts them to sleep inside the hive away from the heat and flames, Geant said. Beekeepers regularly smoke out the hives to sedate the colony whenever they need access inside.

Geant has been looking after the cathedral's three beehives since 2013, when they were installed as part of an initiative to boost bee numbers across Paris. The hives produce around 75 kilograms of honey annually, which is sold to Notre Dame employees.