KARL SCHILLER, a Social Democrat whose tenure as economics minister in the 1960s helped establish his leftist party as a responsible partner in West German politics died Monday age 83 in Hamburg . . . A POWERFUL EXPLOSION rocked a five-story building in Manhattan late Monday, wounding at least 15 people, the New York Fire Department said Tuesday. Police suspect the blast may have been caused by a gas line explosion . . . A HOUSE FIRE in Milwaukee killed four people Monday, three of them young children . . . SMOKE AND ASH pouring from Mexico's Popocatepetl volcano slowed Monday, but disorganization persisted at shelters set up for 50,000 evacuees.