The European Commission has reopened its antitrust investigation into the merger of the Sony and Bertelsmann music divisions, more than three months after it stopped the clock on its probe. The Commission - the European Union's antitrust authority - has now set a new deadline of Oct. 10 for ruling whether to clear or block the deal.

The Commission initially halted its investigation last March as it awaited key data from the two companies on the European music market.

Officials said the investigation was exceptionally difficult, with the market characterized by the strong position of a small number of major players. It was also complicated by changes to the industry, such as digitalization and new consumer behaviors.

The current investigation is very unusual as it is being conducted after the completion of the merger. Last July, an EU court annulled the Commission's original 2004 decision to clear the tie-up that eventually created Sony BMG Music Entertainment, ruling that the Commission had not properly investigated the potential consequences of the merger.

The Commission originally launched the in-depth investigation required by the EU court on March 1 and normally has 90 working days to make a final decision. But the decision to temporarily stop the probe later in the same month (March) was an indication of the expanding depth and breadth of the work involved. The Commission has sought an unprecedented volume of information from the principals to the deal, as well as their competitors and other players in the market.

Extensions of this kind have become increasingly common in the EU and recent changes to the EU Merger Regulation give the staff additional time almost as a matter of course.