The Competition Commission of India (CCI) last year started looking into the complaint, which is similar to one Google faced in Europe that resulted in a 4.34 billion euro ($5 billion) fine on the company, Reuters reported in February.
In mid-April, the CCI decided there was merit in the accusations made in the complaint and ordered its investigation unit to launch a full probe, one of the sources with direct knowledge of the matter said.
That decision, which was confirmed by the second source, has not been previously reported and the order calling the full investigation was not made public.
"It is a strong case for the CCI, given the EU precedent," said the first source. "The CCI has (preliminarily) found Google abused its dominant position."
The probe would be completed in about a year and Google executives would likely be summoned to appear before the CCI in coming months, the source said.