New Delhi, April 1: The Union road and highways ministry has ordered safety audits of all national highway projects and bridges after yesterday's collapse of an under-construction flyover in Calcutta.

IVRCL, the company building the flyover, has carried out many national highway projects and is currently working on two, in Arunachal Pradesh and Andhra Pradesh. Along with these, projects by all construction firms will now undergo safety checks.

Special focus will be on about 1,500 "old" overbridges and underpasses across the national highway network that have been marked out for reconstruction and expansion, said officials in the National Highways Authority of India (NHAI), the Centre's prime road construction arm.

Road transport minister Nitin Gadkari, in notes sent to secretary Sanjay Mitra and NHAI chairman Raghav Chandra today, mentioned these 1,500 bridges, sources said.

Chandra told The Telegraph that "structures and bridges that are half-built and remain unattended for long periods because of delays in project completion" are particularly worrying.

"So, following the instructions from the minister, we are asking all our regional offices and contractors to check out any aberrations that might have crept into the ongoing projects," he said.

Officials in the Union urban development ministry, which had cleared the Calcutta flyover project, had said yesterday that the serial delays in construction could have contributed to a weakening of the scaffolding and, therefore, to the collapse.

The safety checks will be carried out by the NHAI and the National Highways Infrastructure Development Corporation, formed recently to build highways in the Northeast and along the country's borders and strategic areas.

"The (Calcutta) incident has come as a shock for us, as the company has bagged several NHAI projects in states like Arunachal Pradesh and Andhra Pradesh," a senior official in Gadkari's office said.

Ironically, Andhra blacklisted IVRCL as far back as 2009 but that didn't stop the NHAI from handing its Andhra project to the company.

Uttar Pradesh and Jharkhand too have blacklisted IVRCL, the railways have scrapped four projects contracted to the firm, and the navy got into a fight with the company.

But Vijay Chhiber, who retired as road secretary three months ago, said: "We normally blacklist companies facing complaints of using poor construction materials or inordinate project delays, but as far as I can recall, IVRCL was not among such firms."

He added: "However, after yesterday's tragedy, the projects undertaken by it should be thoroughly evaluated."

A director in the ministry's highway division said there had been "no specific complaints against the quality of construction by the company although several of its projects were delayed - but that was because of land acquisition issues or environmental clearances".

The official said that IVRCL had worked on projects worth Rs 2,500 crore for the highway authority in 2011-12 alone, but had not bid for projects over the past four years, possibly because of its poor financial health.

The company is building a 312km trans-Arunachal highway, which has about 50 intersections, two major and 30 minor bridges, and 1,707 culverts. It's being done on a design, build, finance, operate and transfer basis and is nearly complete.

Till 2018, the company will continue to operate and maintain the highway and charge toll on it before handing it over to the government.