Amazon led a $575 million Series G funding round for the startup, which is incorporated as Roofoods Ltd.
As a part of the new movement, the Authority, then, had blocked significant business groups and had undergone investigation on significant companies to regulate the increasing competition in the market.
In response to the CMA's Friday order, Amazon said its Deliveroo investment will help the food app expand its business, "benefiting consumers through increased choice".
The CMA has the power to block any deal between Amazon and Deliveroo if officials deem it would create an unfair advantage and reduce choice for consumers.
Amazon has unsuccessfully tried to launch its own food delivery service in Britain, with Amazon Restaurants UK, but closed the service in December after two years of operation. A CMA spokeswoman could not say when a decision will be made on a formal investigation, but it will use the coming weeks to seek representations from the two companies in which they will argue their position. Both companies, possibly, may overcome the halt if the inquiry finds each company, already, are merged financially.
The deal was not billed as a takeover by Amazon, and Deliveroo has a number of industry competitors such as Uber and Just Eats.
FILE PHOTO: The logo of Amazon is seen on the door of an Amazon Books retail store in New York City, U.S., February 14, 2019. Besides Britain, it also operates in several countries in Europe and Asia, including Germany, France, Italy and Australia.
Deliveroo now has 60,000 riders to deliver meals from more than 80,000 restaurants in 14 countries including Belgium, Italy, Ireland and the United Kingdom.
The vigilance had become tough as Andrew Tyrie joined as the Chairman of CMA in 2018.