NEW DELHI — Health officials in Mumbai are investigating reports that Bollywood superstar Shah Rukh Khan and his wife know the sex of a baby they are having through a surrogate mother.

Sex determination tests are banned in India to stop the practice of aborting female fetuses due to a preference for sons.

Khan was not at home when municipal authorities tried to question him about reports that the woman had such a test, Press Trust of India reported.

A complaint filed by an unidentified, non-governmental organization alleged that Khan and his wife know they are expecting a boy.

Khan has refused to comment.

The 47-year-old actor is popularly known as 'King Khan' in the Indian film industry. He has acted in around 75 Hindi feature films, including many box-office hits. He has also hosted a season of the Hindi version of the game show, "Who Wants To Be a Millionaire?"

He and his childhood sweetheart Gauri have a son and a daughter.

India's 2011 census showed that the country had 914 girls for every 1,000 boys under age 6, a gender ratio mainly attributed to sex-selective abortions despite the ban on prenatal gender tests.