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MEXICO CITY — There are 15,000 police-operated video cameras in this city, about one for every 600 citizens. And there are 93,000 police officers, about one for every 97 people and three times the world average.

Which is why what occurred at the nightclub Heavens After during the night of Saturday, May 25, to Sunday, May 26, is very strange. As its name indicates, this club is a place where the action starts after it has stopped elsewhere. It couldn’t be more centrally located: a few blocks from the Angel of Independence — the city’s main landmark — the U.S. Embassy and the headquarters of the metropolitan police. Yet on that night, 12 patrons between the ages of 16 and 35 — five women and seven men — disappeared. They simply vanished. No emergency calls. No ransom requests.

More than a month later, there is still no news of them. Miguel Ángel Mancera, the city’s new mayor, seems as baffled as the rest of us, and that has turned into the biggest crisis of his young tenure.

For years, while other parts of Mexico were experiencing violence from the drug war, the Mexico City government could boast that organized crime had not managed to sow its chaos here. Not anymore.

All the people who disappeared from Heavens After lived in Tepito, one of the city’s oldest neighborhoods, the breeding ground of too many World Boxing champions and the home of struggling families like the one the American anthropologist Oscar Lewis famously described in his book “The Children of Sánchez.” Tepito is also drug-central and Mexico City’s biggest contraband market for goods like cigarettes and DVDs.

One of those missing is Jerzy Ortiz, 16, the son of Jorge Ortiz, a.k.a. the Tank, who is in prison for extortion and drug dealing and allegedly is the head of one of the organizations that dominate illegal activities in the neighborhood.

The events at the bar happened two days after the killing of a man whom the police say was the top drug dealer of the trendy Condesa neighborhood, which is full of restaurants, bars and art galleries. He, too, was from Tepito.

And on Tuesday, the burned body of Dax Rodriguez, one of the owners of After Heavens, was found on the outskirts of the city.

That’s it for leads. Under pressure from everywhere, Mancera has ordered the city’s attorney general and the parents of the missing to stop talking to the media. “We will let you know when we have something,” he said. The something the rest of us have for now is a suspicion that the disappeared may have been kidnapped because of a dispute between drug organizations.

A year ago Mancera was the city’s attorney general. Then he won the mayor’s post in July 2012 with 63 percent of the votes, in no small part because the capital had largely been spared the drug-related crime wave that the rest of the country has suffered.

His first public-security initiative was “The Shield,” a project with neighboring states to stop drug gangs from settling in the metropolitan area. It added to a feeling of exceptionality among residents of Mexico City — the only place in this country where abortion is legal and gay couples can marry.

But then that one mysterious night in May changed everything.