EU antitrust regulators are set to open a full-scale investigation into Alphabet Inc unit Google’s $2.1 billion bid for fitness tracker maker Fitbit, people familiar with the matter said on Wednesday.

The four-month long investigation will kick off following the end of the European Commission’s preliminary review on Aug. 4, the people said.

Google earlier this month offered not to use Fitbit’s health data to help it target ads in an attempt to address EU antitrust concerns. The opening of a full-scale investigation suggests that this is not sufficient.