The party also expressed apprehensions at the manner in which the Haryana government was probing the issue through a committee with its "hand-picked" officers.
It also took a dig at Congress leaders for maintaining silence in defending Vadra now after their initial enthusiasm and questioned the silence of Congress chief Sonia Gandhi's son-in-law in the matter.
"BJP demands sealing of all the documentary evidence and also an immediate constitution of a free and fair investigation process in the matter," BJP spokesperson Nirmala Sitharaman said.
"We are worried about the evidential material...Which may get mixed up, lost or probably might get completely removed. We demand the entire documentary evidence be sealed in this matter so that if necessary they are available for any investigation. We demand a free and fair investigation in this entire episode of Vadra and DLF," she said.
She said the probe should also look into the manner in which an official (Haryana IAS officer Ashok Khemka) looking into this land deal was transferred and investigation stopped.
Coming out in support of Khemka who was abruptly transferred out for probing the land deal, Sitharaman said, "Here is a classic case which is being played out in front of us - an officer who is trying to see if land in four districts of Haryana has been undervalued...Delivering a transfer order at midnight has just raised a lot of questions." (More)