This was because cross beams that were meant to lock the girders had not been put in place, a team of technical experts investigating the matter found. This, they said in their report, weakened the structure and left it exposed to traffic vibrations and wind force.
Five girders cast between pier 79 and pier 80 in February and March remained free as the required cross beams were not cast, the report said.
The panel -- set up by Deputy Chief Minister Keshav Pradhan Maurya - also pointed to uninterrupted traffic flow on the busy road as the main reason for generating the vibrations.
"There is strong possibility that they (girders) registered some tremblings... the traverse displacement of the girders caused by external forces of movement of traffic and recent storms kept accumulating and they collapsed," read the report, accessed by news agency Presss Trust of India. The report was submitted to Principal Secretary, PWD, Sanjay Agarwal, today in absence of Mr Maurya, who is admitted to a Delhi hospital.
The flyover collapse of May 15 had triggered a blame game between the local administration and the UP State Bridge Corporation, which had built the 2261-metre bridge between Chokaghat and Lahartara at a cost of Rs 129 crore.
The project manager and other officials were suspended and the government also shifted then Managing Director of Bridge Corporation, Rajan Mittal.
Varanasi police chief RK Bhardwaj said around two months ago, an inspection of the construction showed the builders were not following proper safety measures.
Mr Mittal -- who was removed from his post during the term of the Akhilesh Yadav government following complaints and reinstated when the BJP came to power -- had denied the charges. He continues remain the chairman of the UP Rajya Nirman Nigam, another high-profile state government organisation.