SANTIAGO - 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.

The total death toll stood at six, including one person who died at the time of the accident on Thursday evening, 70 hours before the final trapped worker was found.

Codelco Chairman Maximo Pacheco said the state-run miner would convene international experts to investigate the cause and determine "what we did wrong."

The collapse was triggered by one of the largest tremors ever recorded at El Teniente, with the impact of a 4.2 magnitude quake. It is still unclear if the cause was a natural quake in the highly seismic country or mining activity.

"We're the first ones who want to know what happened," Pacheco told reporters at Codelco's offices in the city of Rancagua, near the mine in central Chile.

"This tragedy hits us hard."

President Gabriel Boric called for three days of mourning for the miners. The trapped men were aged 29 to 34 and were employed by excavation firm Gardilcic, according to local media.

Codelco is the world's biggest copper miner and Chile the largest global producer that supplies about a quarter of the world's red metal used in industries from construction to electronics.

Throughout the weekend, dozens of people placed candles, Chilean flags and photos of the trapped workers at a makeshift memorial outside the entrance to El Teniente.

The rescue effort began in earnest on Friday evening, once aftershocks from Thursday's tremor had subsided.

In Codelco's final update on Sunday afternoon on the rescue effort, it said it had cleared 25.5 meters (84 feet) of passages near El Teniente's new Andesita section, removing 3,270 metric tons of material through heavy machinery operated remotely.

Codelco discovered the first trapped worker on Saturday and the remaining four throughout the day on Sunday, working with a rescue team of about 100 people.

Mining Minister Aurora Williams said the Labor Ministry and mining regulator Sernageomin would evaluate when it was safe for operations to resume at El Teniente, Codelco's flagship mine that last year produced 356,000 metric tons of copper.

El Teniente, which is more than a century old and boasts the world's largest underground copper deposit, spans more than 4 500 kilometers (2,800 miles) of tunnels and underground galleries - nearly the distance between Chile and New York - in the Andes Mountains, about 75 kilometers (47 miles) southeast of Chile's capital Santiago.