New Delhi, Oct 22 (IANS): The CBI Wednesday booked three directors of a private firm and officials of the Cabinet Secretariat as well as Special Frontier Force (SFF) for "repeatedly showing favours" in the purchase of high altitude tents.

The Central Bureau of Investigation (CBI) has "registered FIR against three directors of Sai Baba Builders, consultants, unknown officials of Cabinet Secretariat and SFF for repeatedly showing favours in the supply of pre fabricated shelters for SFF at high altitude locations, causing undue gain to the supplier to the extent of Rs.22 crore", a CBI official said.

SFF is a paramilitary special force of India that was created Nov 14, 1962 and is now a unit of the Research and Analysis Wing (RAW), which is India's external intelligence agency.

A daily had reported that the Prime Minister's Office (PMO) had referred the case of alleged irregularities in purchases made by SFF to CBI.

The CBI also conducted searches at three places - two in Delhi and one in Kolkata - against the three directors Wednesday.