TOKYO (AP) — Workers entered one of the damaged reactor buildings at Japan's stricken nuclear power plant Thursday for the first time since it was rocked by an explosion in the days after a devastating earthquake, the plant's operator said. Tokyo Electric Power Co. said workers connected ventilation and air filtration equipment in Unit 1 in an attempt to reduce radiation levels in the air inside the building. The utility must lower radiation levels before it can proceed with the key step of replacing the cooling system that was knocked out by the March 11 quake and subsequent tsunami that left more than 25,000 people dead or missing along Japan's northeastern coast.