Agency sources said a preliminary report has been completed which found that increase in the assets of Mulayam Singh and Akhilesh was primarily because of loans from relatives which were later claimed to be gifts.
They said besides the agency could not find any unexplained increase in the assets of the father-son duo.
The sources added that during the period of 1993-2005, investments by Mulayam Singh and Akhilesh grew manifold which make it difficult to ascertain the exact quantum of alleged disproportionate assets.
CBI Director Ranjit Sinha who was away from the Headquarters last week is back in the Capital and is expected to take a decision on the issue.
The sources said that an inquiry could not be said to have been completed unless a final view is taken by the top brass of the agency.
In many cases, they said, decisions of the investigating teams have been overturned as senior officials had spotted angles which could be probed further.