As the rescue operation at the partially collapsed under-construction tunnel in Uttarakhand entered its fourth day, workers and family members of those trapped staged a protest on Wednesday, reported PTI.

The tunnel on the Brahmakhal-Yamunotri national highway collapsed in the early hours of Sunday, leaving 40 workers trapped inside. The tunnel is part of the Char Dham Road Project to build all-weather roads in Uttarakhand.

The protest began after a plan to insert steel pipes through the rubble to rescue the workers failed on Tuesday evening.

“The Navyuga officials are not talking to us properly, neither there is any actual information of what is happening inside,” Luv Kumar Raturi, a worker, was quoted as saying by The Indian Express. “We are also not allowed to go inside the tunnel. It is the fourth day and nothing conclusive is happening. Those inside are our brothers.”

The tunnel is being constructed by Navayuga Engineering Company Limited under the supervision of National Highways and Infrastructure Development Corporation Limited.

The protesters on Wednesday raised doubts about whether oxygen was being supplied to the trapped workers. This came as rescue officials were forced to dismantle a platform for the auger drilling machine to insert steel pipes through the rubble due to landslides.

“On Tuesday evening, the fresh debris fell where the auger machine had been placed to drill holes in the piled up debris to set in the large diameter pipes,” Devendra Patwal, Uttarkashi disaster management officer, told the Hindustan Times. “Then, again, when the rescuers started drilling through the auger machine a boulder in the debris blocked its way. The teams have been facing many technical challenges.”

As part of their revised plan, the authorities are flying in new equipment from New Delhi to assist in the rescue operations.

“Under plan 2, we are first installing a 125 mm [millimetre] pipe for air, food, camera and communication,” said Bhupendra Singh, the deputy general manager of Rail Vikas Nigam Limited. “That pipe is already 12 metres in. Also, state-of-the-art, American-made horizontal dry drilling equipment with auger is on its way on two Hercules C-130 planes. The planes will make a total of three rounds to carry the equipment.”

He stated that the team was certain that this plan would work. If they face difficulties, they would use conventional drilling techniques with a pipe roof umbrella method. “Under that, we will build an entire tunnel and it will take five to six days as it goes just around 10 metres a day,” said Singh. “However, we are sure it will not come to that and the second plan will work.”

The Uttarakhand government has formed a six-member expert committee to investigate the causes of the accident, ANI reported.

The trapped workers hail from Bihar, Himachal Pradesh, Jharkhand, Odisha, Uttarakhand, Uttar Pradesh and West Bengal.