Some of the 40 Indian construction workers trapped in a collapsed road tunnel for four days have fallen sick as falling debris and technical glitches have delayed the work to free them.

Wide pipes are set to be drilled through excavated rubble to create a passage to free the workers, who have been trapped since Sunday.

Relatives and friends of the trapped workers gathering outside the tunnel in the north Indian state of Uttarakhand have grown frustrated and angry with reports some workers were becoming unwell.

Magistrate Abhishek Ruhela said some workers have sent messages saying they are suffering from fever, body aches, and nervousness.

Medicine has been sent through pipes that were set up earlier to get water and food to the workers.

Two of the workers were reported to have minor injuries from the falling debris.

Around 200 disaster relief personnel are using drilling equipment and excavators to rescue the workers, who are mostly migrant labourers from across India.

Steel pipes 2ft 6in (76cm) wide, which arrived at the site on Tuesday, will be pushed through an opening of excavated debris with the help of hydraulic jacks to safely pull out the stranded workers.

Gaurav Singh, a state government official, said the rescue operation was delayed because of a technical fault in the drilling machine, but a new machine has been installed.

Falling debris also delayed the start of the drilling on Tuesday.

“These are challenges in such rescue operations, but we will overcome them,” said Ranjit Sinha, a disaster management official.

A landslide on Sunday caused a portion of the 4.5km tunnel to collapse about 200m from the entrance.

The construction of the tunnel is part of a flagship federal government project connecting various Hindu pilgrimage sites.

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Region prone to landslides, earthquakes and floods

The region, which is dotted with Hindu temples and sees a huge flow of pilgrims and tourists every year, is prone to landslides, earthquakes and floods.

It has expanded over the years with the massive construction of buildings and roads.

The tunnel collapse follows land subsidence events in the state that geologists, residents and officials have blamed on rapid construction in the mountains.