Sighting in Lachaux, December 9, 2023

Two witnesses noticed powerful flashes of light in the distance, mostly toward the north, on recordings from a surveillance camera. The earliest footage they reviewed was from 21 October 2022. Similar flashes appeared again on several dates: 8 November 2022 (6:15 to 8:15 pm), 8 March 2023 (9:45 to 10:30 pm), 9 May 2023 (9:30 to 10:00 pm) and 9 December 2023 (7:30 to 9:30 pm). One witness described the light as white, while the other found it more orange. It showed up to the northwest, north or northeast. On 9 May and 9 December 2023, the phenomenon was also seen with the naked eye and filmed on one witness's mobile phone. Neither the witnesses nor the camera picked up any sound.

Weather archives of lightning strikes in France showed that a thunderstorm was present on each date and at each time, generally north of the witnesses and around a hundred kilometres away. The GEIPAN's lightning and thunderstorm expert explained that thunder is usually audible out to 30–40 km, sometimes 70 km, whereas from an elevated spot with a clear view, like the witnesses' vantage point toward the north, low lightning or the landscape it lights up can be seen at 150–200 km. This produces the look of a powerful flash on the horizon, similar to what the videos show. However, lightning between clouds is not logged by the detection system, which only records strikes to the ground.

Some uncertainty remained for 8 March 2023 (storms to the west, or about 200 km away) and for 9 May 2023 (storms within 10 km, which the witnesses would normally have recognised). The GEIPAN nonetheless classified the case as A: observation of distant lightning.