The first information report (FIR) was lodged on the basis of a detailed written complaint handed over at the Marine Drive police station by Zinta late Thursday.
But Wadia has said the charges were "baseless" and he was "shocked at the complaint".
An investigating officer said police have started calling witnesses and will also scan the CCTV footage of the alleged incident which took place May 30 in Mumbai during an Indian Premier League (IPL) match.
On Thursday night, Zinta, in a written complaint accused Wadia, whom she dated for five years till 2009, of molesting and abusing her.
Among other things, Zinta has accused Wadia of grabbing her hand and abusing her during a cricket match at Wankhede Stadium here.
Wadia, who along with Zinta co-owns the IPL franchise Kings XI Punjab, issued a statement Saturday denying her allegations.
"I am shocked at the complaint and the allegations made against me are totally false and baseless," Wadia said.
Police may contemplate action against Wadia after questioning witnesses and examining video clips of the IPL match in Mumbai a fortnight ago.
Meanwhile, a delegation of the Maharashtra State Women's Commission led by Chitra Wagh visited the police station Saturday afternoon to ascertain the probe status and action initiated by the police in the matter.
"The police have informed that they have completed most of the inquiries into the incident. Some witnesses and CCTV footage are still to be probed and will be done soon," Wagh told mediapersons.
She said she had demanded that the police immediately arrest Wadia and present him before a court to give justice to Zinta.
In a statement to the media earlier Saturday, Zinta claimed that her intention (behind the complaint) "is not to harm anyone but only to protect myself".
Later Saturday, she issued a detailed statement on her Facebook page 'Real Preity Zinta'.
It read: "I may not be super wealthy and powerful but I have truth by my side and I've worked very hard all my life and tried to earn respect for myself as a self-made professional. It saddens me that no one at work or around ever stood up for me in the past when I was abused and insulted publicly.
"This time I was left with no option but to take this stern step as this incident happened in front of way too many people."
She is sure "the witnesses will speak the truth and I trust and believe that the police will do their job fairly and quickly."
A popular actress, with films like "Sangharsh", "Kya Kehna", "Veer-Zaara", "Lakshya", "Kal Ho Naa Ho", "Kabhi Alvida Naa Kehna" and "Heaven On Earth" to her credit, Preity even turned film producer with "Ishkq In Paris", which released in 2013.
Known as Bollywood's dimpled beauty, she's often frank and upfront about her views.
She added: "Every human being has a limit to how much they can take; some of us foolishly call it strength and try to look ahead focusing on the positives of work and life. All these years I have never said anything about him (Ness) in the media but now I have no choice."
