Calcutta, March 3: An entire deck slab of a flyover built two years ago collapsed with a truck around 4.10am today, shaking to the foundations the trust countless Calcuttans repose in everyday symbols of convenience taken for granted elsewhere.

Three persons escaped with injuries but the cave-in could have had more disastrous consequences had it taken place during the day. The flyover is used by motorists keen to leapfrog a congested spot in north Calcutta while heading to and from the airport.

Two years in the life of a flyover is as goods as factory-fresh and people use such facilities with the same confidence they show when they step into a lift, although how either works is not in their hands.

Moreover, the flyover that collapsed this morning had been hailed as an “architectural marvel” by the state government.

So severe was the impact that a resident who lives over 200 metres away was woken up around 4.10am by what he described as “an almighty shake”.

Closer to the site, Aparajita Prasad, who lives on the seventh floor of an apartment block that overlooks the flyover was jolted out of sleep by an “explosion”.

She could not believe what she saw from her window. “I could only see a cloud of dust. After a few minutes when the dust settled what I saw under the neon lights of the flyover and of the adjoining billboards was unbelievable. A portion of the flyover was missing. I have never seen such a sight in my life before,” said Aparajita Prasad, resident of Rohini.

S. Banerjee, general manager, Mackintosh Burn that built the flyover, said: “The truck that had taken the flyover was carrying 55-60 tonne of stone and had hit the side of the bridge. This bridge does not have railings as is normally witnessed but has concrete walls.”

The force with which the truck hit the wall created a horizontal force that was transferred to the bearings leading to the fall of a 39-metre portion of the flyover, he said.

But the truck driver said he hit the wall after the flyover started to wobble and caved in.

The company has now become a government controlled entity after the government of Bengal has acquired additional 2.5 per cent stake in the company from Mackintosh Burn Co-operative Credit Society Ltd. (MBCCSL) on December 2, 2010 thereby raising its stake in the company to 51 per cent.

Gopal Sardar was sleeping in his hutment nearby when the “earth shook”.

“Along with other youths of the colony, I rushed towards the flyover. I could hear loud cries emanating from the truck. All of them were bleeding badly. We wriggled them out of the mangled driver’s cabin and rushed them to hospital,” Sardar, who drives vehicles for a living, said.

The 1,300-metre flyover transformed the journey to and from the airport, especially, for those residing in south and east Calcutta.

When the flyover became operational in 2011 — not before skipping three deadlines in 2010 — it empowered airport bound passengers to circumvent the traffic snarls at the crowded north Calcutta junction and drive to the airport.

After it came under severe criticism, the then CEO of Calcutta Metropolitan Development Authority Vivek Bhardwaj, had termed the flyover an architectural marvel because of a sharp curve (a bend at the point where it turns an angle of 90 degrees on either side).

A frequent flier in eastern Calcutta said that the flyover had managed to a large extent erase the frightful memories of an era when the particular junction and it’s traffic snarls were a reality.

At least one specialist who introduced himself as a professor from National Institute of Disaster Management in Delhi said that a “bearing failure” could be the reason behind the cave-in.

“I did not detect any damage to the pillars. Two bearings on the inside of the curve are broken while the other two on the outside are intact. While the actual cause of the collapse can be known only after an inspection by technical experts, at this stage it seems that the portion slid off due to load bearing failure,” said the professor of the institute under the ministry of home affairs who visited the spot around 12 noon.