At least 58 people died in a historically massive earthquake that struck the southern coast of Mexico early Friday, toppling hotels and houses and prompting tsunami waves and power outages.

The United States Geological Survey said that a magnitude 8.1 quake hit about 73 miles off Tres Picos, Mexico, along Mexico's southern coast.

Its epicenter was 102 miles west of Tapachula in southern Chiapas state and had a depth of about 21 miles. The quake was so powerful, it sent people fleeing from buildings 650 miles away in Mexico City.

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President Enrique Pena Nieto said the earthquake is the biggest the country has seen in a century. 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.

Chiapas' Gov. Manuel Velasco told Milenio TV that at least three people have been killed in the region and 10 died in Oazaca, close to the quake's epicenter. He said the quake damaged hospitals and schools. Two children also died in Tabasco state.

One of them was killed when a wall collapsed, and the other was a baby who died in a children's hospital that lost electricity, cutting off the infant's ventilator.

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The Pacific Tsunami Warning Center early Friday confirmed tsunami waves in Mexico, with the largest wave so far measuring 2.3 feet.

Smaller tsunami waves were observed on the coast or measured by ocean gauges in several other places. The center's forecast said Ecuador, El Salvador and Guatemala could see waves of a meter or less.

Civil protection officials in Mexico were checking for damage in Chiapas, but the quake was so powerful that frightened residents in Mexico City fled apartment buildings, often in their pajamas, and gathered in groups in the street.

Around midnight buildings swayed strongly for more than minute, loosening light fixtures from ceilings. Helicopters crisscrossed the sky above Mexico City with spotlights.

Zhaira Franco, 35, who was in Mexico City, told The New York Times that she heard an alarm for about 30 seconds before feeling the quake. She said her building swayed so much that it hit the building next door.

"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

The USGS reported a magnitude 5.7 aftershock about 12 minutes later. There have been up to 13 aftershocks.

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.

Lucy Jones, a seismologist in California who works with the U.S. Geological Survey, said such a quake was to be expected.

"Off the west coast of Mexico is what's called the subduction zone, the Pacific Plate is moving under the Mexican peninsula," she said. "It's a very flat fault, so it's a place that has big earthquakes relatively often because of that."

"There's likely to be a small tsunami going to the southwest. It's not going to be coming up and affecting California or Hawaii," she said. "For tsunami generation, an 8 is relatively small."

The Associated Press contributed to this report