With the toll rising to six dead, authorities told the local news agency Diarios y Noticias that hopes were dwindling that eight other miners still missing could have survived the blaze two days earlier.
The mining accident that began with a fire deep in the tunnels late Monday at the remote mine in southern Argentina prompted search teams to rush night scopes and other high-tech equipment to the scene.
The Diarios y Noticias dispatch said searchers advanced several kilometers (miles) underground before they spotted two more victims on Wednesday afternoon.
Authorities said the search group was advancing to the underground chamber where the fire began in the vast coal deposits of Rio Turbio, a mining complex 2,100 kilometers (1,345 miles) southwest of Buenos Aires.
Rescue workers said they hoped the remaining miners had managed to reach several ventilated areas deep in the mine where officials believe the miners may have tried to seek refuge.
President Nestor Kirchner, a three-term governor of remote Santa Cruz province where the Rio Turbio mine is located, traveled Wednesday to the state-run mine.
He had personally monitored rescue reports since Monday's accident.
His public works chief, Julio de Vido, was already at the scene and pledged an exhaustive investigation once the rescue and recovery operations are completed.
While de Vido acknowledged that local reports had cast suspicion on a faulty mechanical belt, he cautioned that it was too early to venture any finding.
An army helicopter clattered above the mine on an overcast, frigid day as army troops helped transport rescue brigades on all-terrain vehicles to the different mine entrances and set up communications equipment for searchers.
``We have provided night vision equipment and the rescue crews are using those now,'' said army Col. Federico Anschutz, speaking with the Telefe television network.
He also said army experts had set up a better communications network after radios malfunctioned underground.
Authorities said they found a total of four bodies late Tuesday not far inside the entry to the vast underground mine complex.
Still holding out hope, worried family and friends maintained a vigil nearby.
At least two air force planes equipped with emergency medical equipment were ordered on standby by military authorities. Two regional hospitals also were put on alert.