More than 30 miles of beaches on Oahu, the most heavily populated island in Hawaii, have been polluted by a spreading oil spill, authorities said. "The ocean current is sweeping it around the island and taking it north," said Coast Guard pollution inspector Richard Vlaun. "It has affected an awful lot of beach." Six beaches on the island posted signs warning beachgoers of the pollution. Sea birds were also reported covered with oil. Heavy seas caused a barge to spill about 1,000 gallons of fuel oil into the sea southeast of Oahu, near Honolulu, officials said.