The Italian police were hunting for a fourth suspect on Sunday after arresting the imam of a mosque in central Italy and two of his aides over the weekend on suspicion of running a ”terror school” that trained children in bomb making and guerrilla combat. The police said they confiscated as many as 60 types of chemicals from the home of the imam, materials that they suspect could have been used for bomb making. All three of the men arrested were Moroccan. The police identified the imam as Korchi el-Mostapha, 41, and his two aides as Mohamed el-Jari, 47, and Driss Safika, 46. The raid was part of a two-year investigation that involved monitoring of telephone and Internet communications. Arturo De Felice, the police chief in Perugia, where the men were arrested, said investigators raided the mosque on Saturday morning. He said the imam’s home was near the mosque. The police said they found computer files including video and documents on weapons training and instructions on how to prepare poisons and explosives, pilot a Boeing 747 and send encrypted messages. The police also said the suspects had contacts with members of the Moroccan Islamic Combat Group who were arrested two years ago in Belgium. The Islamic group is believed to have ties to Al Qaeda and has been linked to the 2004 train bombings in Madrid and the 2003 suicide bombings in Casablanca, Morocco. Chief De Felice said he did not believe that those arrested Saturday were planning an attack but rather were focusing on training. He said he was confident that the fourth suspect would be caught within days.