KOLKATA, India (Reuters) - Police on Friday opened a case of culpable homicide against the company that had been building a flyover which collapsed in Kolkata, killing at least 23 people and injuring dozens.

Rescuers with cranes and jackhammers struggled on Friday to clear shattered concrete slabs and twisted girders from the 100-metre (110-yard) length of the flyover that on Thursday crashed down on pedestrians and vehicles in a road below.

Over 100 people have been rescued, many with serious injuries, but chances of finding more survivors dwindled after authorities removed crushed cars and a bus from the rubble in a teeming commercial district near the city’s Girish Park.

“It is being ensured that there are no more dead bodies under the debris,” S.S. Guleria, deputy inspector general of the National Disaster Response Force, told Reuters Television.

Television channels broadcast images of autorickshaws and a crowd of people suddenly obliterated by a mass of falling concrete.

Chief Minister Mamata Banerjee, whose centre-left party is seeking re-election soon in the state of West Bengal, said those responsible would not be spared and blamed the previous state government, which awarded the flyover contract in 2007.

But she herself faces questions about the project.

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The Telegraph newspaper reported in November that Banerjee had wanted the flyover - already five years overdue - to be completed by February. Project engineers expressed concerns over whether this would be possible, the Telegraph said at the time.

The disaster could play a role in the election in West Bengal, whose capital is Kolkata. It is one of five approaching polls that will give an interim verdict on Prime Minister Narendra Modi’s nearly two years in power.

Indian company IVRCL had been building the 2-km (1.2-mile) Vivekananda Road flyover, according to its website. Its shares closed down 11.7 percent in Mumbai trading on Friday as police announced they had opened a case of culpable homicide.

Police detained seven employees of the company, interviewed bosses at its headquarters in the southern city of Hyderabad and sealed its offices, police said.

“ACT OF GOD”

A senior IVRCL manager drew national condemnation for calling the disaster “an act of God”.

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“We did not use any inferior quality material and we will cooperate with the investigators,” the company’s director of operations A.G.K. Murthy told reporters on Thursday. “We are in a state of shock.”

Years of delays may have led to corrosion to metal elements of the flyover, according to rescuers. Locals said concrete had been poured on the stretch that collapsed the night before the disaster.

Crowds of residents tried to help trapped people. Three cranes worked overnight to clear wreckage and gain access to vehicles in which people were believed to be trapped.

Harrowing news images showed the limbs of a dead man protruding from under a steel girder. Ambulances struggled to reach the scene, hemmed in by buildings.

“Every night, hundreds of labourers would build the flyover and they would cook and sleep near the site by day,” said Ravindra Kumar Gupta, a grocer who pulled out six bodies, together with his friends.

“The government wanted to complete the flyover before the elections and the labourers were working on a tight deadline. Maybe the hasty construction led to the collapse.”