Rescuers have drilled about halfway through fallen debris to reach 41 workers trapped for ten days inside a collapsed tunnel in the Indian Himalayas, an official said on Wednesday.

The men have been stuck in the 4.5-km (3-mile) tunnel in Uttarakhand state since it caved in early on Nov. 12 and are safe, authorities have said, with access to light, oxygen, food, water and medicines.

Rescue workers have drilled through 32 metres (105 feet) of an estimated 60 metres (197 ft) that must be cleared in order to push through a pipe wide enough for the men to crawl out, said Deepak Patil, a retired army officer heading the rescue effort.

First images emerged on Tuesday from within the tunnel, showing workers in white and yellow hardhats standing in the confined space and communicating with rescuers, after a medical endoscopy camera was pushed through a smaller pipeline.

Authorities have not said what caused the tunnel collapse, but the region is prone to landslides, earthquakes and floods.

Efforts to bring the men out have been slowed by snags in drilling in the mountainous terrain.