By Daina Beth Solomon and Fabian Cambero
SANTIAGO (Reuters) - Chilean copper giant Codelco has halted mining at its flagship El Teniente mine and postponed its quarterly results announcement as it continued efforts on Friday to reach five trapped workers following a deadly collapse.
By afternoon, the workers had been trapped nearly a full day without contact following a 4.2 magnitude tremor on Thursday that killed one person at the new Andesita unit of the world's largest underground copper deposit.
Codelco said it would reschedule the release of its first-half financial results, planned for Friday morning, due to its attention on rescue efforts, which were complicated by aftershocks.
"The tunnels are closed; they've collapsed. There's no possibility of even radio communication," El Teniente's General Manager Andres Music told a press conference around midday.
Codelco planned to send remotely operated equipment, similar to robots or drones, to help workers clear material blocking the tunnels once aftershocks subsided in the evening, Music said.
Codelco halted copper mining at El Teniente as part of its emergency protocol, while continuing its processing and smelting operations, said Amador Pantoja, an El Teniente union leader.
Codelco, the world's biggest miner that has been struggling to boost output, has not addressed how El Teniente's production could be affected.
However, Chairman Maximo Pacheco told a press conference that unaffected areas of the mine should be able to operate normally. In the Andesita sector, 300 linear meters were severely damaged, and another 400 linear meters were moderately damaged.
Chilean Mining Minister Aurora Williams said the government would formally order Codelco to suspend all underground operations at the mine, part of protocol for major accidents.
Codelco is investigating whether the incident - which also left nine people injured - was due to natural causes in the earthquake-prone country, or mining activity.
"The event we recorded yesterday is one of the largest events - if not the largest - that the El Teniente mine has experienced in decades," said Music, the mine's manager.
He said neither explosives nor drilling had caused the accident, and that the first subsequent 48 hours would be critical to the rescue effort, for which some 100 people had gathered on site.
PRODUCTION STRUGGLES
Chile's prosecutors' office also opened a criminal probe to determine whether any companies or workers violated safety standards or other regulations.
The five trapped workers were hired by construction company Gardilic, while the man who died worked for Salfa Montajes, also a construction firm, Codelco said.
Chile's Sernageomin mining regulator told Reuters last year that Codelco had been sanctioned 29 times since 2021 and has had seven fatal accidents, with most incidents in project construction.
Andesita is one of Codelco's newest projects at its flagship El Teniente complex and had been due to open in the second quarter this year. Any initial production is still a small fraction of El Teniente's total output, which last year reached 356,000 metric tons.
But delays in its ramp-up, as well as an extended shutdown throughout El Teniente, will make it harder for Codelco to reach its year-end production target, given ongoing challenges at other projects, said CRU analyst Nicolas Munoz.
Andesita is expected to produce 60,000 to 70,000 metric tons a year when it reaches full capacity around the end of the decade, Munoz said.
Codelco last year barely surpassed its production goal, after output hovered at the lowest levels in a quarter century.
El Teniente could potentially make up for the losses in other sectors of the sprawling mine, Munoz said, but Codelco would still face challenges to significantly boost output.
"Rock bursts and seismic conditions raise questions and pose a challenge for the company about how they will manage going forward, especially knowing that these sectors are key to sustaining El Teniente over the next decade," he said.
The Andes Norte unit last year suffered from a rock explosion with the impact of a 3.9 magnitude quake that caused collapses in more than 2,000 meters (6,600 ft) of underground galleries.
No workers died in the accident, but Codelco took a year to recover production in the sector.
El Teniente, which is more than a century old, 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.
(Reporting by Daina Beth Solomon and Fabian Cambero, editing by Deepa Babington, Marguerita Choy and Alistair Bell)
