Mexico City (CNN) -- Seated in a room of the attorney general's office in the western Mexico state of Jalisco, a woman waits to be reunited with her 13-year-old daughter. Two weeks before, the girl had run away from home.

Her mother thought that "she was out there with her boyfriend." But the newspaper that a neighbor took her told a different story: the eldest of her six children belonged to the criminal group of drug traffickers, the Zetas, and had been detained the previous weekend during a confrontation between police and gunmen.

In an interview with CNNMexico, the woman, who asked not to be identified, said she did not know whether her daughter was involved in alleged criminal activities -- although the girl confessed to the contrary.

The woman traveled from the nearby state of Zacatecas to Guadalajara, in Jalisco, to see her daughter. "The first thing I did, when I found out, was try to support my daughter, come for her, to show that she is not guilty of anything, because she is a girl," the woman said. "We all feel very bad over the news, but we know that she is not to blame, she is a girl incapable of doing so much."

In a statement before the public prosecutor and later before reporters, the girl said she had spent a month working for organized crime.

She said that her work -- which paid some $800 for the month -- consisted of keeping track of who entered and left Luis Moya, a community of about 10,000 residents located in the south of Zacatecas in central Mexico.

The girl said that she reported to a 22-year-old woman known as La Chaparra, who has since been arrested by state and federal police.

Guarded by two police officers, each nearly twice her height, the teenager -- wearing jeans and a sweatshirt -- was taken before reporters. Before her sat a table laden with the arsenal allegedly seized in the operation during which she was arrested. Her parents were not there.

The reporters questioned her:

What cartel were you working for? "For the Zetas."

Does your family know this? "Yes."

What did they tell you? "That I should leave."

How much were they paying you? "4,000 (pesos) every two weeks."

Since when? "Since a month ago."

How did you enter? "By necessity."

The girl said that her mother had introduced her to La Chaparra. Nevertheless, she said that she was the only member of her family who was working for the Zetas.

The girl was taken to the facilities of the Jalisco delegation of the attorney general's office, where she remained for three days before being released because the Law of Integral Justice for Adolescents of the State of Jalisco stipulates that only offenders older than 14 are subject to serving time in jail.

The alleged youthful member of the Zetas was taken before the First Court of Minors of Jalisco, who must establish the conditions for her rehabilitation. But she will be able to work toward her rehabilitation at home, under the vigilance of her mother and tutor.

As the only person responsible for her family, the mother said she works 12 hours per day in activities that she prefers not to divulge. She said her schedule had kept her from keeping track of what her daughter is doing after the school day has ended.

The woman said she knows that her daughter skipped her high school classes a few times and had been expelled due to what the school called rebellious conduct. But she said her daughter had vowed afterward to improve, and has gotten good grades -- good enough to be awarded a scholarship by the Mexican government. "She's a very intelligent girl, but -- as with all children her age -- a little rebellious, a little restless, but she is a very good girl," the mother said.

From now on, the mother added, she will be more aware of what her daughter is doing, and she will help with her daughter's rehabiliation.

The employment of children by Mexican cartels is no longer a novelty in the country. Eduardo Guerrero Gutierrez, consultant and security analyst, said that such criminal groups recruit principally young people.

"The youths are not contracted directly by the cartel, rather by groups that work for them, who recruit, train, pay and -- if they show potential -- incorporate them in jobs of greater responsibility to convert them into assassins," he said.

Last month, in the state of Morelos, a 14-year-old boy was sentenced to three years in a Mexican prison and a fine of 4.5 million pesos (about $400,000) for crimes that included homicide, possession of a weapon, kidnapping and organized crime.

Witnesses testified that the boy had tortured and decapitated four men. Linked to the South Pacific cartel, the boy said he had joined organized crime at age 11.

The teenager's age -- and his on-camera description of the slayings -- brought international attention to the case. Analysts said the dramatic example showed how Mexican drug gangs were increasingly recruiting youths.

In Mexico, minors who have committed serious crimes receive lighter sentences than those imposed on adults. Some critics believe that, to dissuade minors from engaging in criminal activity, the law ought to lower the age of criminal responsibility from 18 to 16.