France is investigating suspected tampering with a weather sensor at Charles de Gaulle Airport after unusual temperature spikes affected Polymarket bets tied to Paris daily highs.

According to reports, unknown individuals are suspected of using a heating device, apparently a hair dryer, to artificially raise the sensor reading.

The incidents took place in April, when temperatures suddenly jumped within minutes despite normal weather conditions in Paris.

Météo-France said physical signs of interference were found on one instrument, and an official investigation was opened after one bettor reportedly profited about $35,000.