Kolkata: Problems started with the under-construction Vivekanand Road flyover here during midnight of Wednesday-Thursday when concrete casting was being done, construction workers said. Sunil Sarkar, who was among those doing the concrete casting, said: "The bolt was coming apart as the bucket could not hold it. I think the sunshade in that particular place was made too big." Sarkar, now in hospital after sustaining injury when the flyover collapsed on Thursday, said a technician was called who welded the bolt in place. "Our supervisors assured us that everything was in order and asked us to go ahead with the concrete casting." "The casting continued till noon today (Thursday). When the work was almost complete, the same part caved in and the flyover gave away," said the resident of Murshidabad district.