LONDON — Britain’s competition regulator said on Friday that it had begun an investigation into a $575 million investment led by Amazon in the London-based food-delivery service Deliveroo, the latest effort by a government to potentially check the reach of a technology giant.

In an order, the country’s Competition and Markets Authority said it had reasonable grounds to suspect that Amazon and Deliveroo had “ceased to be distinct” businesses or that they would essentially merge if the investment were to go through.

Work on the investment was ordered halted pending the regulator’s inquiry into whether it posed competition concerns.

In the United States, federal regulators and lawmakers are studying whether Amazon, Facebook, Google and Apple have broken antitrust laws. And their European counterparts, long considered more active in enforcing competition rules, have been stepping up scrutiny as well.