Six miners who became trapped after a tunnel collapsed in Utah are facing up to three days underground as hundreds of rescuers use heavy machinery to dig through rubble to reach them.
Authorities said they had pinpointed the location of the six miners who were digging underground at the mine, run by the GenWal company, around 200km southeast of Salt Lake City at the time of the cave-in.
Despite knowing the men's location, rescue crews have been unable to reach them via a parallel mine shaft because parts of that shaft have caved in.
Rescuers will instead try going through the top of the mountain using a giant drill.
Seismic activity detected at the same time the mine collapsed was probably caused by the cave-in itself and not an earthquake, according to US geologists.
But the National Earthquake Information Center said a final conclusion was still several days away.
The mine's owner has insisted that an earthquake was responsible for the collapse and lashed out at experts and members of the media who have said otherwise.
The earthquake centre detected a tremor with a 3.9 magnitude centred about 1.6 km below the surface.
The question of whether an earthquake triggered the collapse has become a key issue as rescuers race to reach the six men, who have not been heard from since the mine collapsed early on Monday morning.
The miners were declared missing yesterday following the tunnel collapse about an hour after the earthquake was felt.
Four rescue crews and around 200 workers have been deployed in an effort to try and reach the men.
Rescue workers are around 500m away from where the men are believed to be trapped.
