Police in Mexico City have detained three people in the mysterious disappearance of 12 people from a nightclub, the city's attorney general said.

For the first time since the disappearance, Attorney General Rodolfo Rios confirmed there is evidence showing that the missing had indeed been at the nightclub.

The names of the detainees -- one woman and two waiters from the Heavens After bar -- were not released. Officials said they are looking at the link between the woman and the waiters, but did not say what charges, if any, they might face.

Before Tuesday announcement, the relatives of the missing people, one only 16 years old, insisted that they had been kidnapped from an after-hours bar in Mexico City's Zona Rosa entertainment district. But police had said there was no proof that that the 12 had even been there.

"There is evidence that the majority of the youths arrived at Heaven in two vehicles, one private and a taxi, but it is unknown how they left," Rios said.

Still, he said, there is no evidence that an armed convoy snatched the group, as the families say.

The attorney general also upped the number of missing to 12 from 11, saying that another family had come forward.

Not all of the 12 people said to be involved knew each other, but most of them hail from the Tepito neighborhood, a place known for its rough character. That alone has added spice to an already sensational story, leading to speculation that gangs could be involved.

The young people were taken from the Heavens After nightclub on Sunday, May 26, between 10 a.m. and noon, family members say. They were forced into a van and kidnapped, they claim.

A center for missing persons in Mexico will distribute across the country photos and information about the missing young people.

A mass kidnapping would be a significant development because even through the years of drug cartel violence, the capital was a relatively safe place. Recently, however, there is evidence that infighting between local criminal groups is on the rise.

More than 26,000 people have gone missing in Mexico over the past six years as violence surged and the country's government cracked down on drug cartels, according to Mexico's Interior Ministry. Authorities don't have data on how many of the disappearances were connected with organized crime.