So far they have drilled 24 metres, or one-third of the required distance, said Devendra Patwal, a disaster management official.

However, drilling was interrupted on Friday afternoon when some machine bearings were damaged due to broken rocks, according to National Highways Authority Director Anshu Manish Khalko.

Another heavy-duty drill is being brought into the tunnel to continue drilling without interruption, Mr. Khalko said. It is expected to arrive at the site on Saturday.

Rescuers had hoped to complete drilling by Friday evening and create an escape tunnel using pipes welded together.

He said some workers had been feeling feverish and had body aches since Wednesday, but their condition had not worsened. Nuts, roasted green beans, popcorn and medicine were being delivered to them via pipeline every two hours.

Construction workers have been trapped since Sunday when a landslide caused a 4.5km section of the tunnel to collapse about 200 metres from the entrance. The mountainous area is prone to landslides and subsidence.

The site is located in Uttarakhand, a mountainous state dotted with Hindu temples that attract pilgrims and tourists. Highways and buildings have been built continuously to accommodate the growth.

The tunnel is part of the Chardham Expressway, a flagship federal project connecting several Hindu pilgrimage sites.

Trung Kien (according to AP)