A panel of secretaries today referred the issue of residual government stake sale in Balco and Hindustan Zinc to Vedanta Group to an empowered group of ministers (EGoM), which will meet soon to take a decision. "The committee of secretaries (CoS), which met on Wednesday, has reservations over the valuation of Balco as it found the offer conservative, while it also discussed the offer for stake buy in Hindustan Zinc (HZL). The matter has now been referred to EGoM," a source said.