Police said this in an investigation report filed in the special court for anti-corruption cases here along with the charge sheet in the disproportionate assets case against the state Congress leader and his family.
The charge sheet says that Singh's wife, Maltidevi, started trading at Multi Commodity Exchange of India (MCX) in 2008 and incurred losses of Rs 37 lakh in a single year.
This trading was in fact a "face-saving exercise to regularise the ill-gotten money," it says.
Further, there was an unsecured and outstanding loan between Narendra and Bollywood actor Salman Khan, it says.
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The charge sheet also questions Maltidevi's and Narendra's role in the purchase of two flats in a society in suburban Bandra, which were eventually acquired by Salman's parents Salim Khan and Salma Khan.
According to the report, Narendra "forged" 12 stamp papers including two given to film director-producer Anurag Kashyap in 2009 for producing the film 'Udan'.
Sanjay Tiwari, a local activist, had filed a PIL before the Bombay High court earlier, alleging that Singh and his relatives had disproportionate assets worth Rs 320 crore. The High Cort directed the police to conduct a probe.