STOCKHOLM (AP) — Police in Stockholm, Sweden, are investigating whether one of their own is to blame for a security breach that shut down a U2 concert. A police spokesman says they are looking into a suspected weapons offense. An internal affairs unit has been alerted. He says organizers called off Sunday’s concert after someone was not properly searched at a security checkpoint. Swedish media report an off-duty police officer was wrongly allowed to enter the venue with a gun. No one was arrested and no weapon was found in the arena. The concert has been rescheduled for tonight.