Four training grenades were reportedly thrown into the courtyard of a mosque near Paris Thursday, a day after Islamic militants attacked the offices of satirical French magazine Charlie Hebdo.

One of the grenades is said to have detonated, but no injuries have been reported. Police have quarantined the area, but have not said if they have a suspect. No arrests have been made. Authorities say they also have evidence of shots having been fired at the mosque overnight.

This is one of several alleged attacks against mosques in France since gunmen murdered 10 journalists and 2 police officers during a brutal assault on the office of Charlie Hebdo on Wednesday. The attack is thought to have been retaliation for a recently published cartoon caricature of the Islamic prophet Muhammad. Islam strictly forbids graphic representation the prophet, and past cartoons have led to similar attacks.

Two suspects, brothers Said Kouachi and Cherif Kouachi, both in their 30s, were still on the run Thursday. One of the men is believed to have ties to Al Qaeda in Iraq. Reports that the two men have been located in a rural town in Northern France have not yet been substantiated.

Meanwhile, a third suspect, 18, is said to be cooperating with authorities after surrendering to police in the city of Charleville-Mezieres, north of Paris.

The attack on Charlie Hebdo has led supporters of free speech around the globe to rally behind the paper, which plans to publish one million copies of its next issue in defiance of radical free speech opponents.