LONDON (AP) — British antitrust regulators have started investigating Amazon's purchase of robot vacuum maker iRobot, adding further scrutiny to the $1.7 billion deal.

The Competition and Markets Authority said Thursday that it's considering whether the deal will result in a "substantial lessening of competition" within the United Kingdom. In an initial step, the U.K. watchdog invited comments on the deal from "any interested party."

The acquisition is already facing a review in the U.S. by the Federal Trade Commission amid worries about Amazon's growing market power. Consumer groups had voiced concerns after the deal was announced last year that it would further the e-commerce giant's dominance in the smart home market.

Amazon said it's "working cooperatively with the relevant regulators in their review of the merger."

Bedford, Massachusetts-based iRobot, which makes the popular Roomba robotic vacuum cleaners, said it "continues to work cooperatively with both the U.S. FTC and other regulatory agencies in their review of the Amazon-iRobot merger."