By Steve Almasy, Ray Sanchez and Darran Simon, CNN

(CNN) -- Scores were killed in a powerful earthquake Tuesday that rocked Mexico City and surrounding states. The earthquake toppled buildings, sent rescue workers digging through rubble and knocked out power to millions.

At least 116 people died in the magnitude-7.1 earthquake, officials said. Most deaths were reported in Puebla, Morelos and Mexico states, and Mexico City, the capital.

The government said 3.8 million customers in central Mexico had their electricity service interrupted.

President Enrique Peña Nieto said 27 buildings collapsed in the capital, which is about 75 miles from the epicenter, CNN affiliate Foro TV reported.

The quake hit hours after many people took part in drills and commemorative events on the anniversary of a devastating earthquake that killed thousands in Mexico City, more than three decades ago. Residents realized Tuesday's earthquake wasn't a drill when rooms trembled.

Video showed rescue workers in hard hats and civilians in a Mexico City neighborhood combing through two-story high piles of rubble in search of survivors. Some carried away buckets full of debris.

Preliminary reports put the epicenter 2.8 miles (4.5 kilometers) east-northeast of San Juan Raboso and 34.1 miles (55 km) south-southwest of the city of Puebla, in Puebla state, according to the US Geological Survey.

The earthquake struck at a depth of about 33 miles (51 km).

"Anything below 70 kilometers is considered a shallow quake," CNN meteorologist Allison Chinchar said. "That's important, because shallow earthquakes often cause the most damage, compared to the ones that are deeper, regardless of the strength. But this also was a relatively strong earthquake."

Here are the latest developments:

• Education Minister Aurelio Nuño tweeted "all public and private schools in Mexico City are canceled until further notice." He said schools in the states of Puebla and Guerrero also are closed.

• The airport in Mexico City was closed for a time but reopened by evening. There was no damage reported to its runways.

• Local and state officials gave these fatality numbers: 54 in Morelos state, 27 in Puebla state, 27 in Mexico City, and eight in Mexico state.

• The governor of Puebla said on Twitter that there were reports of damaged buildings. Tony Gali urged residents to follow civil protection security protocols.

• Peña Nieto tweeted that he has ordered the evacuation of hospitals that have suffered damage. He also ordered the transfer of patients to other medical units.

• US President Donald Trump tweeted: "God bless the people of Mexico City. We are with you and will be there for you."

Photographer: Moment turns to terror

Adrian Wilson, a photographer from New York City who was visiting his fiancee, was eating in the capital when the earthquake struck.

"The floor gently rocked as if a big truck went by," Wilson said. "It then amplified in waves and the whole room started shaking. The building is from the 1930s and just survived a big earthquake, so I knew I would be OK."

Wilson told CNN: "The doors were flapping open, the windows, everything."

He took a quick video to show his children, he said.

"It's almost a roller coaster ride, where you think, wow, this is kind of cool. But then all of a sudden, you're like this isn't cool at all," he said.

He looked outside and saw helicopters, and burning and collapsed buildings. "Then you realize ... this is no joy ride for anybody."

Ricardo Ramos, a TV producer from Los Angeles, was scouting a location in a Mexico City cafe when the quake hit. He ran out into the street.

"Thank you, God, for keeping us safe once again. We got to experience another terrible #earthquake, this time during a location scout," he wrote on Instagram.

'It was nerve-wracking'

Luis Ramos, who owns an airline business management company, said he was in a meeting near Mexico's main airport when the ground started to shake.

"We evacuated and when we got outside the roads were moving up and down and trees were falling," he told CNN. "It was nerve-wracking. "

Ramos said he got into a car with his driver and went to check on his 99-year-old grandfather, Pedro Cabrero, who lives in a high rise.

"On the elevated roadway, I could see smoke and hear explosions," he said. "I saw a lot of damaged buildings where the exteriors had fallen. I saw some collapsed buildings."

Ramos said his grandfather was safe. After the earthquake, the two drove around the capital trying to find a place to eat. "He tells me he's ready for a tequila," he said of his grandfather.

'Furniture fell over'

The earthquake came 32 years after a magnitude-8.0 earthquake hit on September 19, 1985, killing an estimated 9,500 people in and around Mexico City. That quake left a huge scar on the city, resulting in changes in building codes and greater protections against earthquakes, such as the drills that took place hours earlier.

Dorothy Munoz told CNN that she was watching a TV special on the 1985 earthquake when the earth shook for real.

"A fish tank fell to the floor," the Mexico City resident said. "Decorations around the apartment fell and broke. Furniture fell over."

Munoz grabbed her dogs and raced to the street, where people were told not to return to their apartments until buildings were checked for structural damage and gas leaks.

Tuesday's earthquake came more one week after a magnitude-8.1 earthquake struck off the southern coast of the country, killing at least 90.

"This is one of those moments where we all need to come together," Ramos said.

The-CNN-Wire

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