International expert Arnold Dix on Thursday evening said the auger machine drilling through the rubble of the collapsed Silkyara tunnel in Uttarakhand is experiencing "some difficulties" again.

The remark came just hours after drilling to evacuate 41 trapped workers resumed, following a six-hour setback Wednesday night as the American machine encountered an iron girdle.

It was cut by experts, working in a confined environment, before drilling resumed Thursday.

Earlier, drilling was put on hold from Friday afternoon to Tuesday night when the machine encountered a hurdle.

"Right now the auger machine is experiencing some difficulties, for the third time," Dix to PTI. "We have seen this happen before," he reminded.

He did not elaborate on the nature of "difficulties" this time, and it was not immediately clear that this will lead to any major delay in the rescue operation that has entered its 12th day.

However, he remained optimistic about the success of the rescue effort. He said the work was going on in a cautious manner, as it should.

Dix also warned against rushing as it might "complicate" things.

"Since the trapped workers on the other side of the rubble are safe and fit, not rushing has enormous value because if we rush in a situation like this we might create problems we cannot imagine," he said.

The rescue operation is in full swing with various agencies working on multiple rescue options, he added.

Dix, who heads an international consortium of experts in tunnelling, is in Silkyara to offer advice.

(Except for the headline, this story, from a syndicated feed, has not been edited by staff)