By Sampath Kumar BBC reporter in Madras

Authorities and social activists in the southern Indian state of Tamil Nadu are concerned over the increasing incidence of mothers abandoning their new-born babies.

In the last week alone, four infants were left unattended in different hospitals across the state capital, Madras.

A new-born baby girl found in a government hospital in the city on Thursday was the latest in what appears to be a growing trend.

Although poor mothers in rural areas are often known to do this, it is thought to be a new phenomenon to have hit urban Tamil Nadu.

Legal ban

In the latest incident, a woman who was admitted to the hospital under a fictitious name, gave birth to twins.

Some mothers leave babies in the hospital

Following the death of one of the infants, she is believed to have slipped away leaving the other at the hospital.

Female infanticide is quite common in many Indian villages with poor families giving up their babies.

They fear that raising a girl is just not affordable since they would need to save money for a dowry when she grew up.

A legal ban on determining the child's sex before birth makes it hard for parents to abort the female foetus.

So, unwanted babies are either killed or abandoned.

New concerns

Some unwed mothers throw away their babies to avoid social stigma.

A state-sponsored scheme helping mothers leave their baby girls with a cr�che is believed to have partially helped reduce the numbers of abandoned children.

Tamil Nadu's Social Welfare Minister, Ms Valarmathi, says 650 babies have been left with the cr�che since it was set up seven years ago.

But the apparent increase in abandoned babies recovered in Madras has led to renewed concern.