At least 20 miners have been killed and dozens are still missing underground following a methane gas explosion in a Siberian colliery. Another sixteen miners have been brought up alive - two are in hospital. The accident happened in the Kemerovo district of Siberia in the Kuzbass coalfield region. The authorities said that mine shaft walls collapsed in the wake of the explosion and that there was a failure of electrical and ventilation systems. A massive rescue operation is underway, but so far no contact has been made with the missing miners, who are believed to be 600 metres below ground and up to five kilometres from the mineshaft entrance. Authorities are adopting a cautious approach for fear of gas explosions. **PHOTO CAPTION*** A video grab of a miner outside a colliery where 20 miners where killed after a gas explosion in Siberia's Kemerovo district, April 10, 2004. (REUTERS/RTV Pool)