London (CNN Business) Britain's competition regulator is escalating its investigation into whether Amazon's planned investment in UK food delivery company Deliveroo would reduce competition and harm consumers.

The Competition and Markets Authority said in a statement Friday that it had opened a "phase 2" probe after the companies failed to address its concerns about how the deal would affect the market for online deliveries of restaurant meals and groceries.

"There's a real risk that it could leave customers, restaurants and grocers facing higher prices and lower quality services as these markets develop," Andrea Gomes da Silva, the regulator's executive director, said in statement earlier this month.

Just Eat JSTTY Uber UBER The in-depth investigation could delay the completion of the deal, hurting Deliveroo in the ultracompetitive UK market while giving rivals andEats a boost.

A spokesperson for Deliveroo said the company would continue to work closely with the regulator.

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