Spain arrested two prison inmates Saturday on charges of spreading propaganda for the extremist group known as ISIS or Daesh. Both men, who were out on leave, were in jail for common crimes, the Local reported.

The alleged Islamic State group supporters are a 24-year-old Moroccan national and a 32-year-old Spaniard. They are accused of spreading ISIS recruiting materials, such as videos of executions. One of the men posted a video of himself burning his passport and pledging his allegiance to the group, as many militants have done in Iraq and Syria.

Prison inmates are often at risk for radicalization, particularly from fellow prisoners styling themselves as radical imams. France has tried to counteract this threat by sending moderate imams to preach in prisons, though lack of funding has made it difficult to send imams for longer than a few hours. “Prisons are the breeding ground for radicalization,” Mohammed Chirani, a community organizer in Paris, told Newsweek in February.

Spain has stepped up its counterterrorism efforts after a series of terror attacks rocked neighboring France Nov. 13, leaving 130 dead and several hundred more wounded. The Southern European nation is no stranger to Islamic extremism, and a series of subway bombings in Madrid in 2004, carried out by al Qaeda, left 191 dead. Spanish authorities have arrested 100 people since January on suspicion of being involved in terrorism.

Just days after the Paris attacks, Spanish authorities announced Nov. 18 they were investigating 301 individuals for ties to Islamic terror groups, the newspaper El Pais reported. The number of arrests for Islamic terrorism has quadrupled since 2013, and 45 percent of terrorist suspects arrested in the country have been Spanish nationals, according to the same report. Open cases have also grown by 60 percent in the same period.