UTTARKASHI: The new "high-performance" American auger drilling machine used by the rescue team to save the workers trapped in the under-construction Silkyara tunnel in Uttarkashi for nearly a week, hit a roadblock on Friday.Rescue officials said the high-capacity machine, which started operating a day ago, was able to insert 900mm steel pipes till about 24 metres into the debris till early on Friday, and "work got stalled around 10am due to a likely obstruction encountered while drilling."A team of experts from Delhi also reached the tunnel collapse site for a "geo-physical survey" of the debris.They will use ground penetrating radar (GPR) and "seismic reflection method" to detect the obstacles on the path of the drilling machine.A member of the survey team, requesting anonymity, told TOI, "As some machines and iron garters are buried under the debris, maybe that is causing the obstruction.

If so, we'll need to choose a new path and insert the pipes again."In another significant disclosure, the Uttarkashi district administration said late on Friday that based on fresh inputs received, there were 41 workers trapped inside the tunnel and not 40 as surmised earlier.Uttarakhand tunnel crash: Drilling process inside Silkyara tunnel done upto depth of 25 metre, efforts underway to rescue 40 trapped labourersMeanwhile, Anshu Manish Khalkho, director (admin - finance) of NHIDCL, the central government PSU executing the project, said, "We're in a good situation and can achieve a breakthrough once the next 30 to 35 metres of drilling is completed.

It can happen even earlier.

Four pipes have been inserted and the fifth pipe has been set up for further drilling.

Till now, we are achieving an optimum penetration speed of 1 to 2-metre per hour."On the work being stalled, he said, "Constant use of heavy machines can disbalance the equilibrium of the tunnel's surface.

So, it is important to stop these machines for some time.

Moreover, a machine is unable to push any further as it gets lifted and its bearings may get damaged.

This is only a minor issue.

We're going to start the drilling process again soon."