Eleven people are missing after reports of a mass kidnapping from an after-hours bar in Mexico City's Zona Rosa district. The alleged abduction reportedly occurred 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 one-and-a-half blocks from the U.S. Embassy, the Associated Press reports.

Family members of the missing flooded the streets of the city’s main square Thursday morning, protesting outside the bar and demanding to see the bar's surveillance video.

While police have received 11 missing-person reports, a mother of one of the people who vanished told reporters that residents of the downtown neighborhood of Tepito, where the victims live, thought as many as 15 or 16 people could have been abducted.

Prosecutors slapped closure stickers on the front doors of 

Bicentenario Restaurante-Bar Thursday, with inscriptions saying the city's anti-kidnapping unit was investigating abductions at the site. The closure followed a massive presence of members of a special police intervention unit, many carrying automatic weapons and wearing helmets and bulletproof vests, who blocked off the street in front of the bar and searched the grounds of the bar.

While any leads at this point are just speculation, Isabel Fonseca, whose brother is among those missing, told the Associated Press that 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 cell phone accessories.

Other relatives told reporters they believe waiters and bar employees herded them out to the street around mid-morning before armed men bundled them into waiting vehicles and took them away.

Mexico City's chief prosecutor, Rodolfo Rios, told reporters investigators had been able to gather very little information on the disappearances and that police had not located any employees of the bar and no other witnesses.

"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 and sits in an area that locals describe as a bustling neighborhood.

The city’s apparent mass kidnapping comes not long after the grandson of American civil rights activist Malcolm X was beaten to death at another tough bar in the downtown area.