A Commission spokesman said private hearings with the five companies were expected to begin on Tuesday and to be completed by Friday.
The hearings are expected to be the final opportunity the companies will have to put their cases before the Commission delivers it report, which is due to be handed to DTI secretary of state Patricia Hewitt by August 12.
Other interested parties have been given a deadline of Friday July 4 to respond.
Although there were elements of the statement which each of the protagonists could claim suited their case, most commentators believed Morrisons was now favourite to take Safeway.
Big Food Group chief executive Bill Grimsey echoed the views of many retailers and suppliers when he said: "We particularly welcome the indication that four strong players is the favoured outcome, which favours Morrisons.
"We are disappointed the Commission did not revisit the decision made in 2000 that small-store grocery is a separate market to out of town shopping, although there is an indication that it is looking at smaller Safeway stores separately."
However, Safeway finance director Simon Laffin pointed out: "It's half time. It is a preliminary statement and does not give a clue to the Commission's decision."
>>p32 Hope for all at half time