The U.S. Geological Survey reported the earthquake's magnitude as 8.1, but President Enrique Pena Nieto says it was 8.2, making it the largest in Mexico in 100 years. He also said it was bigger than the one in 1985, when thousands were killed in four Mexican states.
"It was a large-scale earthquake," Pena Nieto said. "It had a bigger magnitude than the one Mexicans knew in 1985."
He said that 62 aftershocks followed the quake and it's possible one as strong as 7.2 could hit in the next 24 hours. Pena Nieto also said that serious damage had been caused and that 1 million customers initially had been without power following the quake, but that electricity had been restored to 800,000 of them.
The USGS said the quake struck at 11:49 p.m. Thursday local time and its epicenter was 165 kilometers (102 miles) west of Tapachula in Chiapas, not far from Guatemala. It had a depth of 69.7 kilometers (43.31 miles).
The quake was so strong that it caused buildings to sway violently in Mexico's capital more than 1,000 kilometers (650 miles) away. Residents fled buildings, many in their pajamas, and gathered in frightened groups in the street. Some neighborhoods remained in darkness after electricity was knocked out.
"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.
Gov. Manuel Velasco told Milenio TV that the deaths occurred in San Cristobal de las Casas. He also said that the quake damaged hospitals and schools.
Its epicenter was 123 km (76 miles) southwest of the town of Pijijiapan, at a depth of 33 km (21 miles). Widespread, hazardous tsunami waves were possible, the Pacific Tsunami Warning Centre said.
The U.S. Tsunami Warning System said the earthquake was a potential tsunami threat to several Central American countries, including the Pacific coastlines of Guatemala, Honduras, Mexico, El Salvador and Costa Rica. It said the threat was still being evaluated for Hawaii, Guam and other Pacific islands.