LONDON (AP) — European Union regulators have opened an in-depth investigation into U.S. tech giant Google’s plan to buy fitness tracking device maker Fitbit. The EU’s executive commission said Tuesday it’s concerned the deal would entrench Google’s position in the online ad market by “increasing the already vast amount of data” the company could use to personalize ads. Google agreed to buy Fitbit in November for $2.1 billion. The European Union’s competition commissioner says the investigation aims to ensure that Google’s control over data collected through wearable devices “does not distort competition.” To allay the apprehension, Google said it said it would not use Fitbit data for Google ads. But the overture wasn’t enough to satisfy the EU.