Codelco says four of the five workers trapped at its El Teniente mine have been pronounced dead, as rescue efforts continue following a powerful tremor that caused the mine to collapse last week.

SANTIAGO, Aug 3 (Reuters) - All five workers at Chile's El Teniente copper mine who were trapped in a collapse last week have been found dead, miner Codelco said on Sunday, as it vowed to investigate the cause and improve safety measures.

All five workers trapped in a collapse at Chile's El Teniente mine were found dead, raising the death toll to six. Codelco will investigate the cause, with questions about natural or mining-related triggers.