Three officials of the IVRCL group, which was building the flyover, were arrested in Kolkata. They include the company's project in-charge in Kolkata, an engineer and an administrative officer. They were among six people detained earlier today. Two others were reportedly detained in Hyderabad by a Kolkata Police team sent to the city where IVRCL is headquartered.

The police have registered a case of murder and attempt to murder against IVRCL following the flyover collapse.

The construction company, under scrutiny over its track record and its debts, defended itself today, hinting at several possibilities including a bomb blast. "The glass was shattered. It could have been a blast," Sheela Peddinti, legal adviser to IVRCL said.

Rescuers worked through the night with cranes, electric saws and jackhammers to look for people trapped in the debris. More than 80 people were rescued. Rescuers now say there is now no possibility of finding any survivor.

62 families living in buildings near the flyover have been asked to vacate temporarily for the safe removal of collapsed debris.

The partially constructed overpass had spanned nearly the width of the Vivekananda Road and was designed to ease traffic through the densely crowded Burrabazaar area.

Within hours of concrete being poured into a framework of steel girders on Thursday, a 100-metre stretch of the overpass collapsed, crushing pedestrians and cars on the road at lunchtime.

The bridge has been under construction since 2009. The company was given an 18-month deadline and a budget of nearly Rs. 165 crore to complete the project but after seven years, only about 60 percent of the work has been done.

Apart from this flyover, IVRCL got 27 projects across India the same year. Last year, it posted a loss of 672 crore and recently, a consortium of banks took over.