A mother's desperate year-long search for her missing baby has revealed a group of doctors and nurses who allegedly tricked patients into believing that their newborns had died, and then sold the children for a few hundred pounds.

The gang was allegedly headed by the owner of a small private hospital in a working class neighbourhood in the east of Mexico City, where Vanessa Castillo gave birth to a girl by caesarean section on 25 October 2008.

Castillo says she saw the newborn and heard her healthy cries before the baby was whisked away from her for routine tests. The next day one of the doctors who had attended the delivery came to her bedside to inform her that the baby had died and had been cremated.

Castillo said that after she was sent home she kept going to the hospital in search of her baby's death certificate and her ashes, but was repeatedly brushed off. A few months later, however, she received an email from the son of the owner of the clinic, saying that her baby was alive but had been sold by his father for 15,000 pesos (about £700).

The police investigation that followed led to the arrest this week of the owner of the hospital, two doctors, a nurse and a receptionist, as well as a psychologist who has admitted to buying the child and who apparently looked after her well.

Once tests had confirmed that Castillo was the mother of the child, she was reunited with her baby girl at an emotive press conference yesterday.

"This is the first time I have seen her since she was born," a tearful Castillo told reporters.

When she was asked about the woman who had bought her baby, she added, "I would like to thank her for looking after my daughter for the last year, but this is not the way to obtain a child."

Police say they have hard evidence of at least one other similar case involving the clinic, and that they are now going through hospital records in an effort to track down more.

"It could be an important number of babies," Mexico City's chief prosecutor, Miguel Mancera, told the Televisa TV network.

"They didn't just steal babies and give them up in illegal adoptions. They also issued false registrations of births at the clinic for babies born without papers elsewhere."

The arrested doctors have denied the charges, claiming that Castillo had gone to the hospital for a very late abortion, and that they gave the baby away for adoption to safeguard its life.

During the past year, Mexico City's authorities have been under fire for not doing enough to track down child trafficking rings.

Local newspapers reported this week that staff from the same clinic had been arrested in 2005 after another mother reported that her baby had been stolen in very similar circumstances. The prompt release of the staff on that occasion has now raised suspicions of past complicity within the prosecutor's office.

In another high profile case involving older children, at least five wards of court from dysfunctional families placed in a private shelter run by an evangelical church have disappeared without trace.