A dead newborn baby was found abandoned inside the toilet of an Indian passenger plane, officials have said.

AirAsia said cabin crew found the baby minutes before they landed in New Delhi on Wednesday.

A 19-year-old woman who was on board the flight has been held by police for questioning.

"A doctor from the medical team at Delhi International Airport confirmed that the baby had been delivered on board," an AirAsia statement said.

The airline said all female passengers were questioned before the woman admitted that she had given birth.

"A 19-year-old acknowledged that she had delivered the baby and was taken to the hospital for medical attention and examination," police official Sanjay Bhatia said.

"She has only told us that she is a sportsperson but refused medical examination or (to give) any more details about the incident," he added.

Investigators are now trying to contact the woman's family to get more details.

The airline said it had informed the country's aviation authority, the Directorate General of Civil Aviation, about the incident.

"We will be assisting in the investigation and cooperating with all concerned agencies," it added.

The mother faces a fine and up to two years in jail.