A car bomb exploded Saturday near a Madrid stadium used to promote the city's bid to host the 2012 Olympics after a warning call by the Basque separatist group ETA, officials said. No injuries were reported. The bomb went off about 7 p.m. at a parking lot outside the Peineta track and field complex, the Interior Ministry said. The parking lot was nearly empty at the time and the blast, which came after a warning call made in ETA's name to the Basque daily newspaper Gara, caused little damage, the ministry said.