SIX men have suffocated in the worst mining accident in Spanish history in the central region of Castilla y León.
An autopsy on the bodies showed that the pit workers, who perished in a gas leak at the Emilio del Valle mine in Pola de Gordón (León province), showed the cause of death to be oxygen deprivation.
All the deceased are aged between 35 and 45, emergency services say.
Five others were rushed to hospital in a critical condition.
The worst-affected, a 42-year-old man, is in intensive care at León hospital on a life-support machine and heavily sedated, but medics say they are 'optimistic and hopeful' about his recovery.
Two others, aged 40 and 55, are now out of intensive care and on a 'halfway-house' ward, where they are under constant observation but not to the extent they would in the ICU.
They are both said to be progressing well and in a stable condition.
Another two men aged 38 and 43 are now on a ward and are expected to be discharged in a maximum of three days.
The tragedy was caused by a methane gas leak, which experts say is usually caused when vegetable matter buried very deeply produces carbon.
They say the gas at such a great depth – between 600 and 700 metres in the case of the mine in León – compresses considerably and is likely to have leaked out after coming into contact with machinery used by the pit workers.