Spanish police arrested on Tuesday eight individuals suspected of ties with the terror cells that carried out the bombings in Brussels’ airport and subway in 2016.

Police in the northeastern region of Catalonia said that the suspected extremists were detained during raids in five towns, including the regional capital Barcelona.

The arrests followed an eight-month investigation in coordination with Belgian police that linked several of the arrested to extremist organizations, as well as organized crime activity. The investigation remains open.

Police said the suspects were Moroccans residents in Catalonia and aged between 21 and 39.

Spanish police have arrested some 200 suspected fundamentalist activists since Spain raised its national security alert to one step below the maximum in 2015.

Thirty-two people were killed at Brussels airport and on a metro station in ISIS-claimed suicide bombings in March 2016.

Bombers Najim Laachraoui and Ibrahim El Bakraoui killed 16 people at Zaventem airport. Around an hour later, Bakraoui’s brother Khalid attacked a metro station near EU headquarters, killing another 16.