Imams in France found to be “preaching hatred” to members of their mosques risk expulsion from the country, according to an Agence France Presse report. Interior Minister Bernard Cazeneuve said Monday that France has deported 40 foreign imams since 2012, a quarter of them in the last six months.

Cazeneuve vowed a crackdown on imams who incite hatred toward non-Muslims following last week’s attack on a French gas factory by a suspected Islamic militant. The terroristic attack was the second in France since the attack on the satirical newspaper, Charlie Hebdo, which left five employees dead and 11 others wounded in Paris.

European leaders say they’ve been fighting radicalization of Muslims in recent months as hundreds of citizens and immigrants leave to wage jihad and join the Islamic State group in Iraq and Syria. “Since the beginning of the year, we have examined 22 cases, and around 10 imams and preachers of hatred have been expelled,” Cazeneuve told AFP.

“Foreign preacher[s] of hate will be deported,” and their mosques “will be shut down” if they are found to be inciting hatred among the faithful, Cazeneuve added.

It’s unclear if Yassin Salhi -- the 35-year-old who confessed during interrogation Sunday to killing his boss and pinning his head to a fence at the gas factory near Lyon -- was radicalized at a mosque in France. The severed head was found with two Islamic flags. Officials later discovered that Salhi had taken a selfie with the head and sent the picture to a phone number that belongs to a French jihadist currently in Syria, the AFP reported.

French security officials had linked Salhi to radical Islamists in France, but investigators believe his act also stemmed from a personal dispute with his employer. “There is no doubt of the personal motivations, but there is a symbolism taken from the most atrocious, abject images of terrorism,” Cazeneuve said.