MADRID (Reuters) – Spanish police said on Saturday they had arrested a 23-year-old man on suspicion of belonging to the Islamic State (IS) militant group, adding that a search of his home found explosive-making chemicals and a list of targets.

Identified only as “A.A.A,” the Spanish citizen was arrested in Parla, a town near Madrid, on suspicion of incitement to commit attacks and terrorist threats, police said in a statement. The case is being investigated by Spain’s high court.

Islamic State claimed responsibility for attacks in 2017 in Barcelona and Cambrils that killed 14 people.

Police said that during a raid on the suspect’s home they had found chemicals that could be used to make the explosive triacetone triperoxide or TATP, an unstable explosive that has been used in several attacks in western Europe in recent years.

They said they had also found a bulletproof vest with shrapnel attached, along with detailed notes on how to prepare explosives and a list of potential targets.

Spanish newspaper El Pais cited unnamed sources saying the suspect had threatened to attack a judge at Spain’s high court.

Police said he was responsible for the Spanish wing of Muntasir Media, which promotes Islamic State and operates internationally to incite followers to commit attacks.

Reporting by Sam Edwards; Editing by Alexander Smith