Police say that 19 people have been killed and another 50 injured after an explosion at the Manchester Arena in northern England, where U.S. pop star Ariana Grande was giving a concert. y. ?* B. c9 w6 N . ^; p8 q3 T3 u4 b3 B* c" P# d8 PThey say they are treating it as a "terrorist incident" as they investigate.