DNA traces have been recovered from the baseball hat worn by the killer of Foreign Minister Anna Lindh, Swedish police say. The breakthrough came five days after Lindh was fatally stabbed in a Stockholm department store. The DNA does not match any samples on the Swedish national database, a police spokesman said. The knife attack came only days before Sunday's euro referendum - when voters rejected membership of the single currency by 56 percent to 42 percent. But the killer's motive remains a mystery, and it is not clear whether the timing was a coincidence. The murder weapon, together with the baseball cap, which has yielded the key DNA evidence, were left behind by the knife attacker as he fled the scene.