Mexico City - A massive earthquake hit off the coast of southern Mexico late on Thursday night, causing buildings to sway violently and people to flee to the streets in panic as far away as the capital city.The US Geological Survey said the quake had a magnitude of 8.0 and its epicentre was 165km west of Tapachula in southern Chiapas state not far from Guatemala. It had a depth of 35km.The US Tsunami Warning System says widespread hazardous tsunami waves are possible on the Pacific coasts of several Central American countries. It said waves were possible within the next three hours for Mexico, Guatemala, El Salvador, Costa Rica, Nicaragua, Panama, Honduras and Ecuador. There was no tsunami threat for the US West Coast.The quake was so powerful that frightened residents in Mexico's distant capital city fled apartment buildings, often in their pyjamas, and gathered in groups in the street. Sections of Mexico City were without electricity."The house moved like chewing gum and the light and internet went out momentarily," said Rodrigo Soberanes, who lives near San Cristobal de las Casas in Chiapas, a poor largely indigenous state popular with tourists.Civil Defense in Chiapas said on its Twitter account that its personnel were in the streets aiding people and warned residents to prepare for aftershocks. But it made no immediate comment about damage.Buildings swayed strongly for more than one minute, loosening light fixtures from ceilings. Helicopters crisscrossed the sky above Mexico City with spotlights. Some neighbourhoods kept electricity while others remained in darkness.In neighboring Guatemala, President Jimmy Morales spoke on national television to call for calm while emergency crews checked for damage. Local radio in the Central American country reported one death, but it could not be confirmed."We have reports of some damage and the death of one person, even though we still don't have exact details," Morales said. He said the possible death occurred in San Marcos state near the border with Mexico.