A joint-venture led by billionaire Gautam Adani is struggling to secure land to rehabilitate poor residents of one of Asia’s largest slums in Mumbai, a government official said, posing a fresh challenge for the ambitious reconstruction plan.

The Dharavi slum, about three-quarters of the size of New York’s Central Park, featured in Danny Boyle’s Oscar-winning 2008 movie “Slumdog Millionaire”.

Its open sewers and shared toilets, close to Mumbai’s international airport, stand in contrast to India’s development boom.

After winning the $619 million bid last year, Adani Group plans to convert the 240 hectare (594 acre) slum into a modern city hub, but it has already faced protests from opposition political parties who say it received undue favours from the state government in awarding the contract.

The group has denied the allegations.

Now there is a new challenge. Only those who lived in Dharavi before the year 2000 will get free homes in the redevelopment and a lot of the land needed to rehabilitate people - at least 580 acres for now - will be to provide housing to the roughly 700,000 people considered ineligible.

To build homes for those ineligible people, the Adani joint venture applied to various local and federal agencies for more land, but has yet to secure any, SVR Srinivas, head of the Dharavi Redevelopment Authority, said.

That’s because such government agencies have their own plans for land they own and are not willing to part with it, he added.

“In Mumbai, getting land is the toughest of things. Physically not a single inch of land has come to us,” said Srinivas.

Asked if he was worried that land acquisition delays will affect the project timeline, he said: “Yes, without land, the project cannot take place, so that is a very critical factor for doing the project on time.”

The Adani Group, which holds a majority stake in the joint venture with the Dharavi Redevelopment Authority, did not respond to an email seeking comments.

The project, which aims to rehouse a million people, is a critical and high-profile project for Adani, who last year faced allegations of business mismanagement and stock manipulation in a scathing report by short-seller Hindenburg Research which he denied.

The project started in March with a survey to determine eligibility and its backers are aiming to complete construction in seven years.

Mumbai is one of India’s most expensive real estate markets where real estate prices are sky-high and land is scarce.

Adani’s group has acknowledged that rebuilding Dharavi presented “colossal” challenges - though he has said he hoped the area in future would produce “millionaires without the slumdog prefix”.