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.

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.

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.