The discovery was made by journalists from the local media outlet Entroncamento Online, who report that they crossed paths with activist Greta Thunberg during a walk through the city.

Rumours had already been circulating that the Swedish activist had travelled to Portugal by train.

The 22-year-old, who was carrying a backpack, reportedly shared with this local news source that she is here for "tourism and work" in the country and visiting "places and people."

The same source also shared a photo of Greta Thunberg in the city.

Greta Thunberg was photographed last week on a train belonging to the Spanish railway company Renfe. Apparently, she passed through Galicia, Spain, and was headed for Portugal.

"Now, on the train from Compostela to Vigo, I have a Nordic girl right in front of me," wrote the passenger who shared the photo on social media.

After the publication of the photograph, several theories were created to justify Greta Thunberg's presence on a Renfe train. According to the Spanish newspaper El Mundo, some said she was going to a climate forum in Spain or even that she was preparing to boycott the famous Christmas lights in the city of Vigo.

However, the Spanish news agency EFE reported that the Swedish activist was accompanied by another young foreigner and that her final destination was Portugal.

Her sighting in Entroncamento confirms the information from the Spanish agency.

Greta Thunberg became known worldwide in 2018 when, at the age of 15, she began a solitary protest in front of the Swedish parliament, holding a sign that read "Skolstrejk för klimatet" ("School strike for the climate").

This will be her second time in Portugal, as she arrived in Lisbon on December 3, 2019, after crossing the Atlantic Ocean aboard a catamaran to participate in COP25 in Madrid. On that occasion, she was received by dozens of activists and the then mayor of Lisbon, Fernando Medina.