Parisian firefighters used DJI drones to track the progression of the Notre Dame fire and to find the best positions to aim fire hoses. By flying DJI Mavic Pro and Matrice M210 drones over the Notre Dame cathedral, firefighters were able to get essential data for taming the flames.

Notre Dame de Paris was severely damaged by the fire that ravaged its roof, spire, stained glass window, and pipe organ. Police say the fire was likely an accident, potentially caused by ongoing renovation work.

Fire brigade spokesman Gabriel Plus told local media that the drones were instrumental in saving the cathedral’s structure. “The drones allowed us to correctly use what we had at our disposal,” Plus said in comments translated from French. Firefighters also relied on the Mavic Pro’s visible light camera and optical and electronic zoom, according to DJI’s director of public safety integration, Romeo Durscher, who has Parisian contacts. The Verge has reached out to the Paris Fire Brigade and the police for comment.

Both Durscher and DJI comms told The Verge that as far as they knew, thermal cameras weren’t used by the firefighters, even though thermal technology would definitely have helped in this case. Thermal cameras have become increasingly useful in recent tech, such as the military version of HoloLens and Parrot’s new thermal cam add-on for its folding quadcopter.

Typically, drones aren’t allowed to fly in Paris and are geofenced to prevent any flying. The restrictions were removed by DJI to cooperate with authorities’ purposes, the company confirmed to The Verge. Any drone operator can request that geofencing be unlocked, but they may require credentials to unlock a particularly high-risk area.

While DJI didn’t train or gift the firefighters with the drones, it did promote its technology. A DJI spokesperson said that firefighters “have now integrated and digested out technology so they can fully adopt it in search and rescue missions...[and] in extinguishing fires like what we saw in Notre Dame.”

“The mission was delicate and they intelligently called for the Parisian Police Drone Unit cell, which is a dedicated team of professional drone pilots ready to intervene in critical missions,” the spokesperson added. The drones were borrowed from France’s culture and interior ministries, as firefighters still don’t have their own drones.