International tunnelling expert Arnold Dix on Saturday said the auger machine engaged for drilling through the rubble at the Silkyara tunnel has busted with rescuers considering other options, including vertical and manual drilling, to bring out the 41 trapped workers.

"Augering is finished... the auger is broken, destructed," Dix told reporters in Silkyara.

The auger machine faced repeated obstructions over the past few days while drilling through the rubble to prepare an escape passage for the trapped men.

When asked about other options such as vertical or manual drilling, Dix said all options are being explored.

"Every door we are trying to open has its advantages and disadvantages. We are going to deal with the mountain and we don't know which of the doors it is going to let us open. We are trying to adjust," he said.

Ensuring the safety of the trapped men and the rescuers is the goal of multiple agencies engaged in the operation, he said.

"The mountain is still unstable. We have had one collapse, we could have more," Dix said, adding rushing could cause more problems.

The tunnelling expert said his daughter is also a miner and his heart is with the trapped workers.

The multi-agency rescue effort began November 12 when a portion of the under-construction Silkyara tunnel on Uttarakhand's Char Dham route collapsed following a landslide, trapping the 41 workers inside.

Drilling at the collapsed portion of the tunnel to rescue the trapped men was halted on Friday night after the auger machine faced a hurdle, apparently a metal object.

Before the brief period of drilling on Friday, 46.8 metres of an 800-mm-wide steel pipe had been pushed into the drilled passage. The collapsed stretch is estimated to be about 60 metres long.

A six-inch-wide tube for supplying food and other essential items to the workers had travelled 57 metres.

With one hurdle after another preventing the auger machine from carrying out horizontal drilling for laying steel pipes through the rubble, the option of manual drilling is being considered for the remaining stretch of 10 to 12 metres, an official said.

Manual drilling, however, takes more time, he said.

Efforts are also being made to create a vertical escape passage, officials said.

On Saturday morning, a big drilling machine was moved towards the hill above the tunnel where two lowest elevation spots have been identified by experts for vertical drilling.

A 1.5-km access road to the top of the tunnel has already been built by the Border Roads Organisation (BRO) as the option of vertical drilling has been on the cards for some time.

Vertical drilling is a more time-consuming and complicated option that demands more exactitude and caution due to narrower space on top of the tunnel roof, Dix had said a few days ago.

With repeated obstructions impeding the rescue operation, the trapped workers' family members appeared to be gradually losing patience.

"For the last two days, we are being assured by the officials that they (trapped workers) would be rescued soon but something or the other happens and the process gets delayed," said Devender Kisku from Bihar's Banka whose brother Virender Kisku is among those trapped.

The workers are in a built-up two-kilometre stretch of the tunnel. They are being sent food, medicines and other essentials through the six-inch pipe.

They have been talking to their relatives and doctors through walkie-talkies.

Except for the headline, this story has not been edited by The Telegraph Online staff and has been published from a syndicated feed.