Updated 5:40 p.m. EST

(Bloomberg) -- A powerful 7.2 magnitude earthquake strucknear Mexico City, toppling buildings and extinguishing lights asthousands of people fled.

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The temblor was the nation’s second major earthquake this month,and struck 32 years to the day after a temblor with an 8.0magnitude killed thousands in the city.

The disaster closed the airport and stopped trading on theMexican stock exchange.

Smoke plumes, fallen concrete, shattered glass

The quake ravaged the far-flung region ofmore 20 million people, and images showed structures suddenlylosing integrity and collapsing into billowing dustclouds.

Smoke plumes rose near the financial thoroughfare of Paseo de LaReforma, which was flooded with people — many of them wearinghard hats — as buildings swayed. Fallen concrete and shatteredglass littered the streets, and at least one building collapsed inthe Roma neighborhood.

The death toll was uncertain. The governor of Morelos state said42 were dead there, but the tally was unknown in the denselypopulated national capital and elsewhere.

“I was working when I felt the whole building shaking,”said Luther Beatriz Ramirez, a governmentworker. “Everything started falling. It was like it was inruins.”

“We ran out of the building; we were really scared.”

She left behind her keys and wallet in an office suddenlylittered with ceiling tiles and dirt.

People asked to leave buildings

President Enrique Pena Nieto is returning to Mexico City fromOaxaca, he said in a tweet. Interior Minister Miguel Angel OsorioChong on Twitter asked people to leave their buildings. Pemex, thestate oil company, said it had activated its security protocol.

Worried that the quake could add to the economy’s woes,investors sold Mexican assets, with the iShares MSCI Mexico CappedETF dropped 0.6% at 3:20 p.m. in New York. The Mexico peso fell toa session low of 17.83 to the dollar.

Seismically active nation

Mexico is one of the world’s most seismically active nations,sitting at the intersection of four major crustal plates, accordingto the U.S. Geological Survey.

The epicenter of Tuesday’s temblor was in Puebla, outside thecapital, according to European Mediterranean Seismological Centre.The quake came hours after emergency drills regularly held on theanniversary of the 1985 disaster.

On Sept. 7, a temblor hit offshore near Chiapas state with amagnitude of 8.2, according to the Geological Survey and Mexico’sNational Seismological Service. Tuesday’s quake was much nearer tothe capital.

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“This was so much worse than the one a few weeks ago,” Ramirezsaid.

It was the country’s second major quake this month. On Sept. 7,a temblor hit offshore near Chiapas state with a magnitude of 8.2,according to the U.S. Geological Survey and Mexico’s NationalSeismological Service.

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