BRUSSELS, Feb 21 (Reuters) - EU antitrust regulators are set to charge Alphabet unit Google with breaching EU rules aimed at checking the power of Big Tech after proposed changes to its search results failed to address their concerns and those of their rivals, people with direct knowledge of the matter said.

The shares dropped 0.9% in morning trading.

The European Commission has been investigating Google for potential breaches of the Digital Markets Act since March last year.

One probe focuses on whether Google favours its vertical search engines such as Google Shopping, Google Flights and Google Hotels over rivals, and whether it discriminates against third-party services on Google search results.

The imminent charges concerned this issue, the people said.

The other investigation takes aim at potential limitations that hinder app developers from informing users about offers outside the Google App Store free of charge.