The Competition Commission has asked for filing of fresh application with respect to German major Bayer AG's proposed $66 billion buyout of Monsanto.
The deal, announced in September 2016, would create the world's biggest seed and pesticide firm.
A source at the Competition Commission of India (CCI) said the regulator has asked for re-submission of application with regard to seeking approval for the Bayer-Monsanto deal.
Specific reasons for seeking fresh application could not be immediately ascertained.
CCI can ask for filing of fresh application in cases of mergers and acquisitions citing lack of adequate information and certain other ground.
When contacted, a Bayer spokesperson said the process in India is going its regular course and "we are in dialogue with the Indian anti-trust authority in terms of the completeness of the data package".
"We are unaware of any rejection of the application for approval of the agreed merger. Please understand that we are not commenting on further details," the spokesperson said in a statement.
Mergers and acquisitions beyond a certain threshold require approval of the CCI.
German chemical and pharma major Bayer and global biotech player Monsanto have presence in India, with the US firm selling genetically modified (GM) cotton seeds in the country for more than a decade.
As per the earlier notice filed by Bayer before the CCI in October 2016, the "proposed combination raises no competitive concern in any of the overlap products".
In India, both entities have presence in production and sale of vegetable seeds, cotton seeds as well as in production and sale of non-selective herbicides, according to that notice.
After months of negotiations, Bayer and Monsanto in September last year announced signing of a definitive merger agreement. Under the deal, Bayer would acquire Monsanto for $ 128 per share in an all-cash transaction, which translates into an aggregate value of $ 66 billion.