This article originally appeared on NPR:

Among the sweeping changes France is proposing in the aftermath of this month’s terrorist attacks in Paris are new measures to fight Islamic radicalization in its prisons. It is an enormous problem brought into starker relief because two of the suspects in the attacks earlier this month were products of the French penal system.

Cherif Kouachi, one of the brothers behind the attack on the offices of Charlie Hebdo, went from petty criminal to violent jihadist after just 20 months behind bars. There, he also met a Muslim convert named Amedy Coulibaly — who went on to help the Kouachi brothers in the Paris attacks.

The problem of radicalization in French prisons starts with numbers. More than half the people in French prisons today are Muslim — and that has made it easy for radical Islamists to target new recruits.

“The U.S. problem that you have with high rates of Afro-American and Hispanics populating the prisons seems to be like now we have a high rate of Muslims living in the prisons,” says Laila Fathi, a Muslim activist in Paris who lives in the 19th arrondissement, not far from the housing projects where Cherif and Said Kouachi grew up. “The problems are similar.”

Perfect Environment For Radicalization

Many inmates convert to Islam or rediscover their Muslim roots behind bars. Some do it for protection, some for camaraderie; others, just to fit in.

Read the full story at NPR.