The Archaeological Survey of India (ASI) is carrying out a scientific survey in the Gyanvapi complex. Advocate Vishnu Shankar Jain, representing the Hindu side in Gyanvapi Mosque case, on August 06, informed that he pointed out a hollow sound beneath the central dome which is now under scrutiny. "Yesterday, a detailed study of the western wall was done. The grass in the area from the western wall to barricading was removed. The `tahkhana` was cleaned and exhaust is being installed. I pointed out a hollow sound beneath the central dome, it is being investigated. An area beside the central dome, which is covered artificially, was also pointed out. So, investigations are going on. This is a long investigation and it continues gradually," he said while speaking to ANI.