It is a crisp winter morning and the area around Notre Dame is sealed off as it has been since the fire last April that devastated the cathedral.

Those in the know, however, especially those with the keenest of eyes, might spot some small movement high up to the south of the stricken and blackened structure.

The bees of Notre Dame, whose escape from the inferno seemed almost miraculous, are thriving and conserving their energy ready to produce honey this summer, just as they have every year since they took up residence on the sacristy roof in 2013.

Nearly 10 months after the Paris cathedral was ravaged by fire, the three colonies are healthier than ever, according to their beekeeper.

Sibyle Moulin, who looks after the hives, spoke to the Guardian after she visited them for the first time in six months. Access to the site is restricted because the severely damaged 13th-century stone structure is still unstable and there is a risk from lead particles from the roof that was turned into dust in the blaze.

Facebook Twitter Pinterest The fire in April 2019 destroyed the cathedral’s famous roof structure, which was known as ‘the forest’ because it contained so much wood. Photograph: Ian Langsdon/EPA

Moulin, who had to undergo a health and safety course to resume visits to the honey bees, said the 30-45,000 insects in the three hives are absolutely fine.

“There’s nothing wrong with them at all. The behaviour of the colonies is perfectly normal,” she said. “They’re not very active at this time of the year, but that’s how it should be. They seem fine.”

When fire tore through the cathedral last year, most people feared the bees, which can number up to 50,000 per colony, had perished.

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Moulin’s company, Beeopic, received calls of support from well-wishers all over the world, who were moved by reports that the bees had not abandoned their queens in the face of danger, but had gorged on honey and hunkered down to protect their colonies.

Although untouched by the flames which destroyed the cathedral’s famous roof structure, Moulin says she was initially worried the heat might have damaged the hives, given their position on the sacristy roof on the south side of the cathedral and approximately 30m (98ft) below the main roof. Another concern was that firefighters, whose priority was to control the fire, might have disturbed them in their frantic efforts to put out the blaze.

“Of course, my first thought was for the cathedral itself. My second was for the bees. I kept watching the television footage of the fire but the captions at the bottom always hid the sacristy roof, which is below the main roof, so I couldn’t see if they’d been touched,” Moulin said.

Play Video 0:15 Notre Dame bee colonies 'healthier than ever' nine months after blaze – video

Drone footage in the aftermath of the fire showed the hives were intact, but it took several weeks of detective work to establish if the colonies had survived the proximity to temperatures estimated to have reached 800C(1,470F) at their peak.

“An ounce of hope. The three hives are still in place … and visibly intact,” Nicolas Géant, head of Beeopic, tweeted hours after the fire was put out. “As for the occupants … the mystery remains. All that smoke, heat, water.

“We will have to see if our brave bees are still with us as soon as we’re given access to the site, which may take some time,” he added.

Two days later, Géant announced: “Our bees at the Notre-Dame de Paris Cathedral are still alive.”

Moulin says beekeepers had to piece together clues in film footage taken of the cathedral.

“We examined satellite images and we saw the hives were intact and hadn’t been knocked over and there were no puddles of wax underneath them. As the wax melts at around 70C we knew they hadn’t been affected by the heat. We weren’t worried about the smoke, because we use it to sedate them so we knew they’d just go to sleep around the queen.

Facebook Twitter Pinterest Moulin with the unharmed beehives on the sacristry roof three months after the fire. Photograph: Courtesy of Beeopic

“Then we were sent some film from some of the people working on securing the cathedral and we could see bees going in and out of the hives. We studied their behaviour and saw they were carrying balls of pollen on their feet which meant they were building up stocks of protein to feed the young.

“As soon as we knew there were baby bees we knew it meant the queens were fine since they were producing them.”

It was good news, but Moulin could not be 100% sure of the health of the colonies until she was given permission to visit the devastated cathedral in July, three months after the fire.

“They didn’t seem to have been affected at all. Of course, there’s lots of noxious material all around them, including the lead dust, but they’re not like children; they won’t be licking walls or touching anything other than flowers. The only thing they might come into direct contact with that might be contaminated is the water they drink.”

In July, Moulin retrieved 66kg of honey from the three hives, samples from which have been sent to laboratories in Canada to be tested for lead.

Beeopic maintains the hives and bee colonies, but the honey produced from those on the roof of Notre Dame, and the 350 other hives in Paris that the company looks after – of a total of 700 dotted around the city – belongs to the owners of the buildings on whose roofs they sit, including that of Louis Vuitton on the Champs Elysées and the nearby Grand Palais on the north bank of the Seine.

The urban honey bees, of the Brother Adam Buckfast variety, were developed for their mild temperament in the 1920s by a Benedictine monk. The Notre Dame hives were installed on the cathedral roof in 2013 as a gesture to promote biodiversity.

There are also hives managed by other companies on the Paris Opera buildings, the Comédie Française, Coca-Cola’s French headquarters and several banks.

Facebook Twitter Pinterest In the aftermath of the fire, the Beeopic team studied footage and photographs such as this of the cathedral for clues as to whether the bees had survived or not. Photograph: Courtesy of Beeopic

Moulin, who normally visits each hive at least once a month, hopes to remove the queens from the three Notre Dame hives this summer and replace them with younger royals. The queen bees can live for five years, while their worker bees have a lifespan of around 45 days.

“We usually do this every year because when the queen bee is older there is a tendency for the colony to swarm, which tends to frighten people in the city, so we try to avoid it. The problem is that anything leaving the site has to be washed down and decontaminated, and I can’t see myself putting the bees into the shower,” she said.

“At first the authorities wanted us to remove the hives, but they’ve seen [the cathedral through the catastrophe and they’re still there, so it seemed more intelligent to leave them alone.”

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