New Delhi, India CNN — Rescuers on Tuesday successfully drilled through to 41 men trapped inside a collapsed Himalayan tunnel, as a weekslong evacuation effort fraught with uncertainty enters its final stretch.

The men have been trapped since November 12 when the part of tunnel they were helping to construct in India’s northern Uttarakhand state gave way, blocking their only exit with more than 60 meters (200 feet) of broken rock, concrete and twisted metal.