Air quality tests in a section of a Mexican coal mine where as many as 26 miners could have been working have shown there is not enough oxygen to sustain life, it was announced early today.

Rescue workers were burrowing through debris clogging a Mexican coal mine early today, a desperate effort to free 65 miners who had been trapped for more than a day by a gas explosion.

A gas explosion today in a northern Mexico coal mine trapped 66 miners below ground with a limited supply of oxygen, government and company officials said.