Conflans-Sainte-Honorine – 18 July 2026: Beneath the murky surface of the Seine, a search reaching back years is underway. Gendarmerie divers are examining sunken cars near Conflans-Sainte-Honorine that were discovered during sonar surveys. The town is located in the Yvelines department, directly on the border with Val-d’Oise. For investigators, the wrecks are not merely scrap metal on the riverbed, but possible clues to unresolved fates.
The operations are part of the LETHE project. The acronym stands for wreck location, hydrographic analysis and investigations. The initiative is led by Yohan Gérard, an Adjudant-chef and commander of the Gendarmerie’s river brigade in Conflans-Sainte-Honorine. The aim is to create the most accurate possible map of vehicles lying in French rivers and bodies of water – and to systematically assess whether a discovery could be linked to an old missing-person report.
The process often begins above the water: sonar equipment detects unusual structures on the bottom, after which divers and a remotely operated underwater vehicle inspect the find. Currents, mud and poor visibility make this work difficult. Teams therefore document a vehicle’s position as precisely as possible before it is recovered or subjected to further forensic examination. This is intended to prevent potential evidence from being unnecessarily altered.
According to Franceinfo, four human bodies have been discovered since the project began, within less than a year. However, this does not allow any conclusion to be drawn about a specific suspicion of criminal activity. A car may have ended up in the water as a result of an accident, suicide or a violent crime. In each individual case, the responsible investigative authorities and the courts decide on the next steps.
The Gendarmerie notes that the search is deliberately designed as a long-term effort. Numerous vehicles are believed to lie in rivers, lakes and canals in France, with their exact locations not yet recorded. Particularly in old missing-person cases, such a discovery can provide new investigative leads: through licence plates, vehicle identification numbers, personal belongings or establishing the timing of a disappearance.
LETHE works with the unit for serial and unsolved crimes at the Nanterre Judicial Court, as well as the Gendarmerie’s DIANE unit for cold cases. The cooperation is intended to ensure that new discoveries are not assessed in isolation, but compared with existing case files. For relatives of missing people, this can be distressing. At the same time, there is hope that, after many years, it may at least bring certainty.
The work underwater remains an investigative effort without quick answers. Not every wreck leads to an identification, and not every discovery solves a case. But the systematic search changes the view of those cars that lay unnoticed in the mud for a long time: they may become silent crime scenes, but also places where unanswered questions can finally be examined.
Sources
- Franceinfo
- National Gendarmerie – Gendinfo