Rescuers in Uttarakhand temporarily suspend work after hearing ‘large-scale cracking sound’.

Indian rescue workers have paused efforts to reach 40 men trapped in a collapsed highway tunnel over fears of more cave-ins.

Rescuers temporarily suspended work on Friday after a “large-scale cracking sound” was heard while trying to restart a drilling machine, the National Highways and Infrastructure Development Corporation (NHIDCL) said.

The sound created “a panic situation” for rescuers and there was a “strong possibility of further collapse”, the NHIDCL said.

Excavators have been removing debris since Sunday after a portion of the under-construction tunnel in the northern Himalayan state of Uttarakhand caved in.

Rescue efforts have been hindered by falling debris and the repeated breakdown of drilling machinery.

The trapped men have been supplied with light, oxygen, food, water and medicines from the outside and are able to communicate via walkie-talkie.

NHIDCL director Anshu Manish Khalko on Friday warned that the rescue operation “may take time”.

The 4.5km (3 mile) tunnel is being constructed between Silkyara and Dandalgaon to connect the Hindu shrines of Uttarkashi and Yamunotri.

The project is seen as one of the most ambitious undertakings of Indian Prime Minister Narendra Modi’s government.

Authorities have not given a reason for the collapse, but the region is prone to landslides, earthquakes and floods.

Accidents on large infrastructure construction sites are not uncommon in India.

Earlier this year, Indian authorities evacuated hundreds of people from their homes in Joshimath town, also located in Uttarakhand, after buildings in the area popular with pilgrims and tourists developed cracks.