Police in Dortmund are investigating several far-right suspects for an attack on a blogger on Sunday afternoon. Police in Dortmund detained 13 people on Sunday, including far-right extremists already known to the police. All 13 were later released, however, as authorities did not have grounds to hold any of them in custody, a police spokesman told dpa on Monday. Police have determined that the attack by masked men on the blogger was clearly committed by right-wing extremists, the spokesman said. The young man was slightly injured and had his camera stolen during the attack. The police spokesma…