The elevated road was being constructed as one of the connectors to the new terminal building of the Mumbai airport to the opening of the road leading to Marol Naka.
The construction is being undertaken by the GVK-controlled Mumbai International Airport Limited (MIAL) with Larsen and Toubro (L&T) as the contractor.
Three employees of a company were arrested in connection with the collapse of a portion of the under-construction bridge, police said.
The arrested Pechi Muttu Subramaniam (27), Subbaya Velu Shravanal (34) and Lakhbir Nirmal Singh (27) were supervisors of the site and employed with Larsen and Toubro company, which had taken up the construction work of the bridge, they said.
The three were booked under sections 304 (II) (culpable homicide not amounting to murder), 337 (causing hurt by act endangering life or personal safety of others) and 338 (Causing grievous hurt by act endangering life or personal safety of others) of the Indian Penal Code sections, they added.
The labourers were launching a segment through the cantilevering method of construction when it slipped causing the entire span, or the slabs between two piers, to dislocate and come crashing down. The accident took place at about 11pm on Wednesday night inside a barricaded area opposite the Hyatt Regency hotel near the airport. The span had about three segments.
"We have been working on this for three years and have finished 90 percent of the work of launching spans. There are only a few spans yet to be launched now. Launching in this particular area was left because there were some slum encroachments here that were not removed until recently," said an official from Larsen and Toubro on the condition of anonymity.
The MIAL has contracted work to Larsen and Toubro to build a mesh of six elevated connectors to the swanky new terminal building, expected to start international operations by the end of this year.
The first connector runs from the Sahar elevated road, which will take traffic to and from the Western Express Highway, towards the new terminal building. Another one is to return to the elevated road from the new terminal. The third and fourth connectors will provide access to commuters from the new terminal to the Andheri-Ghatkopar link road and to the Ambassador circle. The fifth and the sixth connectors will link the elevated road to the ground level.
While work on the connector to the Andheri-Ghatkopar link road, on which the accident took place, has been stopped till the debris is cleared, work on the other connectors will continue.
"An investigation to find out what exactly went wrong will go on. We will resume work on this connector as soon as the debris is cleared, which should take a couple of days. The accident will not impact the deadline of the project in anyway," the official said. While the 2-km Sahar elevated road, which was constructed by the Mumbai Metropolitan Region Development Authority (MMRDA) is ready, the construction of the connectors is expected to be completed along with the new terminal building. The entire elevated network will be opened to traffic once the terminal building starts operations.
Meanwhile, the Sahar police station arrested Supaiyya Velu Saravan, the L & T site engineer, Lakhwindar Singh Nirmal Singh, a foreman, and Pechi Mutthu Subramaniam, the company supervisor of sub-contractor SP&SJ Constructions and booked them under sections 336, 337, 338, 304 (A) and 114.
The three labourers who were killed in the accident were 44-year-old Ram Balidas Chandrikadas from Bihar, 30-year-old Jaichand Mandal and 26-year-old Santosh Das, both from West Bengal.
The fire brigade was contacted at 11.30 pm after which eight fire brigade engines rushed to the spot.
The six injured were rushed to the neighbouring Seven Hills hospital, Cooper hospital and Holy Spirit hospital. Two of them were discharged after administering basic first-aid.
Of the others, two are critical and are on ventilator at Seven Hills hospital.
"The rescue operations started almost immediately as the Marol fire brigade is very close to the construction site. Within an hour and a half, all the victims stuck in the debris had been rescued and were rushed to the hospital," the head of security at the construction site said.
The road is always barricaded and no unauthorized persons or vehicles are allowed to enter, he said, adding the labourers are also always seen using safety gear.