President Guillermo Lasso, a conservative ex-banker, is betting on mining to diversify the country's income streams.

"Three mine employees were in the fine ore storage area when a cave-in occurred," the company said.

The bank for decades held more than 300 tonnes equivalent of gold, but between 2015 and 2017 the government began using the precious metal as a collateral for loans with international banks.

Embryonic plans to nationalize mining, the creation of a one-chamber Congress, water rights, and protections for indigenous territories are some of the more edgy motions the assembly will discuss.

The initial capital requirement at Escalones is $438.4 million, followed by a sustaining investment of $192.5 million over the 20-year life of the project.

Las Bambas, which produces 2% of the world's copper supply, has said it will have to suspend production on February 20 if the road is not cleared by then.