“The situation remains difficult,” regional governor Vasily Orlov said on social media after visiting the scene.
He has introduced a regional state of emergency and said there has still been no contact with the trapped miners.
Authorities have said they are some 125 metres (more than 400 feet) underground.
Orlov said rescuers from neighbouring regions were also involved in the operation.
Anatoly Suprunovsky, deputy head of Russia’s Emergency Situations Ministry, said a fresh team of experienced rescuers from Siberia’s Kuzbas mining region had arrived to help on Wednesday, bringing more specialised equipment.
The ministry posted a video of workers trudging through a light layer of snow in the giant remote mine – wearing white helmets with headlamps. They joined a team of more than 100 other rescuers already working at the site.
‘Rat hole’ miners to the rescue: how trapped India tunnel workers were saved
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Officials have already opened an investigation for a suspected breach of safety rules. Lax safety measures have often led to deadly accidents in Russian mines and factories.
The Kremlin said on Tuesday, President Vladimir Putin “gave the order to take all necessary measures to save the miners”.
Authorities have posted aerial photographs showing the extent of the rescue mission in the remote mine surrounded by deserted steppes.
Orlov said earlier on Wednesday that rescuers had begun drilling a hole to try to reach the miners.
“Even if the passage does not lead to people, it will be possible to lower a camera into it to assess the situation and lay communication lines,” he said.
There was still “no communication with the miners”, he added. But officials believe they are alive, and Orlov said the trapped group are workers from other regions.
State-owned Izvestia newspaper quoted a relative of one of the miners, who said she was from Sibay – a small town in the Urals region of Bashkortostan region.
“From our town, from Sibay, there are four people there,” the woman, named as Rimma Akhmadeyeeva told the paper.
“The town is small, everyone knows each other. My phone is exploding and on social media [people are] writing, supporting [us],” she added.
“We still hope for a good end, that they are alive. Because they are banging on a pipe, and they are given extra ventilation.”
On Tuesday, Russia’s Emergencies Minister Alexander Kurenkov said: “People who are under the rubble know that people are coming to help them.”
The rescuers were trying to work at “maximum speed” to get through “100-200 metres” every two hours.
Accidents at mines are relatively common in Russia. In 2021, an accident at a coal mine in Siberia claimed the lives of 40 miners.