PCI chairperson Justice Markandey Katju appointed Rajeev Sabade to inquire into the facts of the case, the version of the Maharashtra government, journalists and asked him to submit a report at the earliest.
"Sabade held talks with Patil and Singh," said a statement by the Mumbai Marathi Patrakar Sangh, from where he is operating.
Any organisation or individual wishing to submit information or memorandum to the panel could do so during regular office hours, the statement said.
The incident triggered outrage across the country and was condemned as despicable and shameful stirring memories of a similar attack on a paramedic last December in New Delhi that led to nationwide protests.
Political parties, media associations and Bollywood have joined the common people in demanding harshest punishment to the culprits of the crime in a city which is seen as safe for women.