The apparent mass abduction purportedly happened sometime between 10 a.m. and noon on Sunday morning just off the Paseo de la Reforma, the city's main boulevard, near the Angel of Independence monument and only about 1 blocks from the U.S. Embassy.
The incident was the second recent high-publicity blemish for the city's largely unregulated entertainment scene, coming 20 days after the grandson of American civil rights activist Malcolm X was beaten to death at another tough bar in the downtown area.
Calling for authorities to find their loved ones, family members marched Thursday morning from the Interior Department building to the Zocalo, the city's main square. Later they protested outside the bar, which bears a sign that reads Bicentenario Restaurante-Bar, and demanded to see the bar's surveillance video.
"How could so many people have disappeared, just like that, in broad daylight?" said Josefina Garcia, mother of Said Sanchez Garcia, 19, her only son. "The police say they don't have them, so what, the earth just opened up and swallowed them?"
She said her son wasn't involved in any criminal activity, and worked at a market stall selling beauty products.
City prosecutors said they had received 11 missing-person reports, but Garcia said residents of the tough downtown neighborhood of Tepito where the victims live thought as many as 15 or 16 people could have been abducted.
The known missing include six men, most in their 20s, a 16-year-old boy and four young women.
While no clear motives had been revealed in the attack, residents of Tepito said there has been a wave of abductions of neighborhood young people in recent months that could be related to organized crime activities. Tepito is the center of black market activities in the city, where guns, drugs, stolen goods and contraband are widely sold.
Mass abductions have been rare in Mexico City, but are common in parts of the country where drug cartels operate and are fighting with rival gangs over territory.
Prosecutors slapped closure stickers on the front doors of the Mexico City bar Thursday, with inscriptions saying the city's anti-kidnapping unit was investigating abductions at the site.
Isabel Fonseca, whose brother is among those missing, said a man who escaped told her that masked men arrived in several white SUVs and took the group away. She said her brother, Eulogio Fonseca, is a street vendor who sells cellphone accessories.
"We want them alive," Fonseca said. "They went out to have fun; they are not criminals."
Mexico City's chief prosecutor, Rodolfo Rios, said investigators had been able to glean very little information on the disappearances.
Relatives believe the youths were at the club, which they said is called "Heaven," around midmorning Sunday, when waiters and bar employees herded them out to the street and armed men bundled them into waiting vehicles and spirited them away.
Rios said police had not located any employees of the bar and no other witnesses had presented themselves.
"We aren't sure what exactly occurred," he said. "No witness has come forward to say anything about any armed gang."
The bar is down a side street from two high-rise office buildings that look out on Reforma and sits across the narrow road from beauty salons and a sushi restaurant.
Guillermo Bustamante, owner of one the beauty parlors, said the street bustles every Saturday morning with people coming and going from the bar.
"Every time we arrived on Saturdays, we would see weird people coming out of that bar," Bustamante said. "There would be many Hummers parked outside and men walking out with a woman on each arm."
Bars of questionable character are often allowed to continue operating, even though drugs may be sold inside and the businesses frequently violate rules governing closing times, parking and serving alcohol to minors.
Malcolm Shabazz, grandson of the late Malcolm X, died May 9 in a fight that erupted after he and a friend were presented with a $1,200 bill at a seedy bar near Plaza Garibaldi, a gathering place for mariachi bands in a rough neighborhood in the downtown area. Two waiters at the bar have been arrested in connection with Shabazz's death.
In June 2008, police raided another Mexico City bar to investigate drug and alcohol sales to minors. A stampede ensued as panicked youths rushed for the exits and police tried to stop them. A dozen young people died in the stampede.
Associated Press writer Adriana Gomez Licon contributed to this report.