Britain’s competition authority on Wednesday said it had “serious” concerns over US online giant Amazon’s investment in Deliveroo, the app-based firm delivering restaurant meals.

The Competition and Markets Authority (CMA), revealing the conclusions of a preliminary probe, warned that competition could be stifled for delivery of both online restaurant food and groceries.

UK-based Deliveroo announced in May that Amazon was the largest investor in a $575-million funding round.

The CMA on Wednesday said that competition could be harmed “in two ways” as a result of the deal.

“Firstly… the deal could damage competition in online restaurant food delivery.”

And “the CMA is concerned that the deal could also damage competition in the emerging market for online convenience grocery delivery, where the two companies have already established market-leading positions”.

Created in 2013, Deliveroo has grown to delivering meals to clients in more than 200 cities across 12 countries.