The death toll in Kolkata flyover collapse has raised to 24 as rescuers worked through the night in the Girish Park area.

The flyover was under construction when it collapsed suddenly on March 31.

Hopes of finding more survivors trapped under the collapsed bypass are fading in the Indian city formerly known as Calcutta.

The 1.2 mile-long flyover started construction in 2009 and missed several deadlines for completion.

Indian police have opened a case of culpable homicide against the company in charge of the construction, IVRCL.

Reports say five of the construction company’s officials have been detained for questioning and its headquarters in the southern Indian city of Hyderabad have been sealed off.

The company said it would co-operate with investigators. However one of its senior officials said in a news conference that the collapse had been “an act of god” as the company had a good safety record.

Officials said more than 90 people have been rescued, some of whom are in hospital in a critical condition.

SS Guleria of India’s National Disaster Response Force told the Associated Press that the rescue operation was in its “last stage” and that “there is no possibility of finding any person alive”.

It is not clear how many people may be still trapped under the debris.

Rescue workers have struggled to get cranes and other machinery through the narrow and congested streets of Burrabazar area where the incident happened.

The cause of the disaster was not immediately clear, but safety issues such as lack of inspections and the use of substandard materials have plagued construction projects in India.