A preliminary investigation into the alleged Islamist terrorist attack in the German city of Solingen has left key questions about the Syrian suspect unanswered, but 400 leads are being followed up, a top official said on Thursday. The interior minister of the German state of North Rhine-Westphalia, where last month’s knife attack which killed three people occurred, said it is still unclear when Issa Al H. became radicalized. Herbert Reul told the Interior Affairs Committee of the state parliament that he could have been radicalized in his home country, via the internet, in his refugee accommo…