By Leo Kelion
Technology desk editor
Publishedduration4 AugustshareSharenocloseShare pagelinkCopy linkAbout sharingimage copyrightReuters
The European Commission will carry out a full-scale probe into Google's takeover of Fitbit.
The announcement follows a preliminary review, and threatens to derail the purchase of the fitness-tracking firm.
It comes despite Google's offer last month to not use Fitbit's health data for ad targeting.
Google's parent company Alphabet agreed a $2.1bn (£1.6bn) takeover of the wearable tech firm last year. However, the deal has yet to be completed.
"The commission is concerned that the proposed transaction would further entrench Google's market position in the online advertising markets by increasing the already vast amount of data that Google could use for personalisation of the ads it serves and displays," the regulator said.
The watchdog said its investigation should be completed by 9 December.
In response, the tech giant said it would cooperate with the process.
"We appreciate the opportunity to work with the European Commission on an approach that addresses consumers' expectations of their wearable devices," blogged Google's devices chief Rick Osterloh.