India\'s richest man Mukesh Ambani faces a possible federal probe into the construction of his 27-storey luxury home -- one of the most expensive private residences in the world.The Maharashtra state government is considering whether federal investigators should look into alleged irregularities over the sale of the land on which the home was built, Indian media reported on Tuesday.The Reliance Industries chairman, who according to Forbes magazine is the world\'s ninth richest man with a $27-billion fortune, moved into the 570-foot (174-metre) tower last year.\"Antilia\", on upmarket Altamount Road in south Mumbai, reportedly has six floors of parking, swimming pools, a ballroom, a cinema and three helipads.Maharashtra Minority Affairs and Wakf minister, Mohammed Arif Naseem Khan, told the state assembly on Monday that the 4,532 square metre (48,782 square foot) plot had originally been reserved for the education of Muslim children.Wakf in Islamic law is property or land reserved for religious or charitable purposes.The plot was sold to Ambani by the Currimbhoy Ebrahim Khoja Orphanage Trust for 215 million rupees ($4.77 million) in 2002, the minister said.The deal was approved by the Mumbai Charity Commissioner but the minister said permission was not obtained from the Maharashtra State Wakf Board, which oversees the maintenance and administration of Wakf property and land. The dispute over the sale -- a widespread problem across India and particularly in big cities like Mumbai where land is scarce -- has been rumbling since 2004 when the Wakf board asked Ambani why the land should not be returned to the charity.The opposition leader in the state assembly, Eknath Khadse, of the Bharatiya Janata Party (BJP), on Monday claimed that the plot was actually worth five billion rupees.A Reliance Industries spokesman told AFP that the matter was between the Wakf board and the orphanage and had nothing to do with the company.