German police have detained a suspect with "Islamist links" following a bomb attack on the bus of the Borussia Dortmund football team. Prosecutors also said one of the three explosive devices contained metal strips. Two letters claiming the attack on Tuesday evening were being investigated, they said. Prosecutors are treating the blasts as a terrorist attack but say the precise motive is unclear at present. Chancellor Angela Merkel on Wednesday said the attack was "an appalling crime" and praised the fans of both teams for coming together.