Citing anonymous sources, Reuters said it had reported in February that the CCI had begun its probe last year.
In July last year, the European Union hit Google with a fine of €4.34 billion for an offence similar to the one the CCI is investigating.
Following initial investigations, the Indian anti-trust watchdog decided by mid-April that there was merit to the allegations and ordered a complete probe.
The source of the complaint was unknown, the news agency said.
India has fined Google once before, levying a penalty of 135.86 crore rupees (about US$21.1 million) for "abusing its dominant position in online general Web search and Web search advertising services in India".
This was in February 2018, with the CCI saying at the time that the fine had levied following complaints by two websites in 2012: matchmaking website Bharat Matrimony (Matrimony.com) and the non-profit Consumer and Trust Society.
The CCI can fine a company up to 10% of its turnover in the previous three financial years for abusing a dominant market position.
New Delhi-based anti-trust lawyer Gautam Shahi told Reuters that Google’s earnings from its Chrome browser and search engine could be taken into account when calculating the fine. These earnings are not disclosed by Google.
In March, the EU fined Google for alleged abuse of its AdSense advertising service, and told the company to fork out €1.49 billion (A$2.38 billion) for breaching EU anti-trust rules.
In July last year, the EU fined Google €4.3 billion for allegedly breaching anti-trust rules over its Android mobile operating system..
In June 2017, Google was fined €2.42 billion for allegedly abusing its search engine dominance to give illegal advantage to its own comparison shopping service. Google has appealed against the three EU fines.
Contacted for comment, a Google spokesperson told iTWire: “Android has enabled millions of Indians to connect to the Internet by making mobile devices more affordable.
"We look forward to working with the Competition Commission of India to demonstrate how Android has led to more competition and innovation, not less.”