The Swedish activist was detained by Dutch police during a protest against fossil fuel subsidies in The Hague, where she and other activists, including Extinction Rebellion members, blocked a main road, prompting a tense standoff and repeated police interventions.
Francisco Antonio Agostinho Aniceto, aged 60, was last seen on Thursday at 4 pm.
Luxembourg witnessed the start of a significant logistical operation on Wednesday and Friday, marking the first two of three transports tasked with transporting rotor blades through the country.
Luxembourg police officers have had a busy 24 hours addressing various incidents reported by residents.