The news was reported by the governor of the province of West Flanders, Carl Decaluwé, who quoted was in the Belgian press as saying that the young people were infected on holiday in the Algarve between 2 and 12 September.
About half of these 67 infected young people took part in a stay organised by the Belgian tour operator Summer Bash, which specialises in trips for young people aged 16-24, while the rest rented a private house for their holidays.
According to Carl Decaluwé, "the number of infected young people is likely to increase" as the Belgian authorities have not yet been able to trace all contacts of those who tested positive for Covid-19.
In all, 130 young Belgians spent the first fortnight in Portugal on holiday with the tour operator Summer Bash, and the company recommended testing and quarantining.
Most of these young people are from the cities of Waregem, Tielt and Roeselare in West Flanders, the Dutch part of Belgium.
"I suspect that they have not fully followed the restrictive measures," said the Mayor of Waregem, Kurt Vanryckeghem, also quoted by the press.
Like the metropolitan area of Lisbon and northern Portugal, the Algarve is included in the Belgian Ministry of Foreign Affairs' traffic light system, which means that screening and quarantine are only recommended on return to Belgium.