The flyover connecting EM Bypass with VIP Road, a portion of which had collapsed in March 2013, was closed for an indefinite period on Tuesday evening after an agency studying its health noticed cracks in “critical positions”.

The flyover, which enables commuters bound for the Bypass from VIP Road or the other way round to avoid the snarl-hit Ultadanga crossing, was closed around 7.50pm. As a consequence, traffic was hit on large stretches of both the Bypass and VIP Road.

Government officials said a team would inspect the flyover on Wednesday afternoon and evening.

An official said the cracks were noticed on “pier as well as girder”.

“The cracks didn’t appear good to us. Hence, we decided to close the flyover,” the official said.

The Delhi-based agency that spotted the cracks has been hired by the Calcutta Metropolitan Development Authority (CMDA), the custodian of the flyover, to scan the structure.

A police officer said all VIP Road-bound vehicles from the Bypass were being diverted through the Hudco/Ultadanga crossing on Tuesday evening. All Bypass-bound vehicles from VIP Road were using the old bridge to access the slip road leading to the Bypass.

All airport-bound buses from north Calcutta were diverted to Jessore Road through the Shyambazar five-point crossing. “People should take other routes and, if possible, avoid taking the old bridge to avoid snarls,” the officer said.

A CMDA official said the agency whose engineers were scanning the flyover had told them about the cracks during a review meeting earlier this month but did not recommend closure.

“The experts were monitoring the cracks continuously since then. After an inspection on Tuesday, they felt that the Bypass-bound flank should be closed to traffic,” the official said.

“Cracks were noticed in critical positions. Keeping in mind the safety and security of commuters, the CMDA, senior government officials and the police decided to keep both flanks closed till further orders.”

The official said the agency was doing “an all-round inspection” to understand the nature of the cracks or how dangerous they were.

A portion of the flyover had collapsed in March 2013 and fell into the Kestopur canal. An investigation revealed that faulty bearings were responsible for the collapse. Bearings help transfer the load of vehicles on the flyover down to the piers or columns.

The flyover was reopened in September 2014.

The urban development department, under which the CMDA functions, formed an “expert committee on bridges” after the collapse of the Majerhat bridge in September last year. The committee had made a preliminary inspection of multiple bridges and flyovers in Calcutta and recommended a more detailed study for many of them.

The CMDA then floated tenders and hired agencies with expertise in bridge monitoring for the study.

A member of the “expert committee” told The Telegraph that further investigations were needed to understand the seriousness of the cracks.

“We have to see whether the cracks are serious or not. If possible, remedial measures will be taken while allowing traffic. Else, the flyover has to remain close till the measures are taken,” the member said.