A strong earthquake rocked northern Chile on Thursday, causing panic among the population, authorities reported. There were no immediate reports of deaths or injuries. The quake, which had a preliminary magnitude of 5.5, struck at 4:31 p.m., said Carmen Fernandez, deputy director of the government's Emergency Bureau. Hernan Vargas, a regional director for the bureau, said the epicenter was east of the port city of Tocopilla, 1,550 kilometers north of Santiago. Tocopilla is in the Andes mountains, "which allows us to say that no danger exists of a tsunami," he said. The tremor was felt along a 700-kilometers stretch of Chile's narrow territory, between Copiapo and Tocopilla, he said. It was felt near Chuquicamata, the world's largest open-pit copper mine. "Panic was widespread here, and we are still checking but we have no reports of victims or damage," said Tocopilla Gov. Jorge Peralta. He said power and phone lines were cut but were gradually being restored.