Almost 72 hours after a massive mound of garbage crashed onto a three-storey building at Moshi near Pune city of Maharashtra, authorities have almost broken the collapsed upper slab in a complex and challenging operation to reach eight persons still believed to be trapped under the debris.

8 people are still believed to be trapped under debris as a massive mound of garbage collapsed onto a building in Pune (ANI)

Around 15 excavators, including specialised demolition machines, are engaged in the operation being carried out by the National Disaster Response Force (NDRF) and other agencies, officials said on Saturday.

A senior official said the NDRF is making every effort to complete the rescue operation by late Saturday night, even as emotions ran high as relatives of the trapped persons are losing patience.

However, the nature of the collapse, described in engineering parlance as a "cantilever fall", huge volumes of garbage and debris accumulated around the collapsed structure, leaving very little space for heavy equipment to operate safely, officials said.

A three-storey building located over the waste-to-energy plant at Moshi in Pimpri-Chinchwad industrial township caved in after a portion of the legacy waste dump crashed onto it on Wednesday afternoon, trapping around 18 individuals under the rubble.

In almost 72 hours since the rescue operation was launched, nine people have been pulled out alive, while one body has been retrieved from the debris.

With no survivors being pulled out over the last two days, relatives of the trapped persons are losing their patience, questioning the pace of the rescue operation.

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Pointing out complex structural and technical challenges in the rescue efforts, officials said the operation is in a critical stage.

The rescuers first have to remove unstable portions of the damaged structure before attempting to access the floors where the victims are believed to be trapped, a senior official said.

"Around 15 excavators, including specialised demolition machines, are engaged in the operation being carried out by the NDRF and other agencies.

"The upper slab has almost been broken, and debris removal is underway. Once that is completed, work on breaking the lower slab will begin. We are making every possible effort to safely rescue the eight trapped persons," said Pimpri Chinchwad Municipal Corporation Commissioner Vijay Suryawanshi.

Responding to concerns raised by relatives about the pace of the operation, Suryawanshi said there was "absolutely no delay" in the rescue effort.

"The NDRF is conducting the operation very systematically, as per its experience and established protocols, while working with utmost speed," he said.

Explaining the challenges, the commissioner said the building had suffered what engineers describe as a "cantilever fall", causing two or three front slabs to collapse one on top of the other.

"The trapped persons are believed to be in the front portion where these slabs have come together. The slabs have to be removed very carefully to ensure the victims can be rescued safely, and that is why the operation is taking time," he added.

Suryawanshi said Chief Minister Devendra Fadnavis reviewed the rescue operation on Friday and directed officials to expedite the effort while ensuring that the trapped persons are rescued safely and their families are provided reassurance and support.

"According to the NDRF's preliminary assessment, the first slab has already been broken, while the second slab is expected to take more time to remove before rescuers can reach the location where the victims are believed to be trapped," he said.

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Pimpri Chinchwad Municipal Corporation (PCMC) PRO Kiran Gaikwad said all civic agencies continued to work round-the-clock, deploying additional heavy machinery to expedite the rescue mission.

"Today is the fourth day. The rescue and search operation is continuing non-stop. All the agencies of the municipal corporation are deployed here. Several machines are pressed into service, including two demolition excavators operating on new technology. They were brought to the site yesterday. We want to rescue the people trapped inside at the earliest," Gaikwad told reporters.

He said the operation had reached a critical stage, with rescuers first having to remove unstable portions of the damaged structure before attempting to access the floors where the victims are believed to be trapped.

Gaikwad said the rescue teams are facing significant technical challenges because a huge volume of garbage and debris had accumulated around the collapsed structure, leaving very little space for heavy equipment to operate safely.

"It is very important to prepare adequate working space around the debris so that the machinery can reach the site and function efficiently. A large number of machines, vehicles and personnel are engaged in removing the garbage and debris. We are carrying out the rescue operation with utmost caution while trying to reach those trapped inside," he said.

Meanwhile, responding to reports that the first and second floors of the building were unauthorised, the PCMC Commissioner said a probe would be conducted.

The anguished relatives, who have been at the site since Wednesday, have started questioning the PCMC.

"It has been four days now. When will the trapped people be rescued? Think about those who are trapped inside. We demand that the rescue operation be expedited," said a woman.

Another relative alleged that the work is slow.

"We are not even sure that those who are trapped under the rubble are alive or not," he said.

A man whose brother has been trapped under the debris said that the waste removal work is currently underway.

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Addressing the concerns raised by relatives, the civic chief said officials have been in constant touch with them.

"They have been here since Wednesday. We understand their emotions and share their pain. They are members of the Pimpri Chinchwad family, and we are deeply saddened by the tragedy that has befallen them," he said.

PRO Gaikwad added: "We are making every possible effort to save the people trapped inside. We understand their emotions and stand with them. We also want to bring those trapped out as soon as possible."