(Bloomberg) -- Shares in Australia’s Resolute Mining Ltd. plunged more than 30% on Monday after the gold producer confirmed its chief executive officer and two other employees were unexpectedly detained in Mali late last week.

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Resolute, which operates the Syama mine in the country, had been in talks with mining and tax authorities in the capital Bamako, as the country’s military-controlled leadership pushes for increased revenue from its mineral resources. Mali is Africa’s third-biggest gold producer and is looking to the metal to offset sanctions that threaten key sources of government revenue.

Resolute’s shares were down around 28% near noon in Sydney, valuing the miner at just over A$1 billion ($660 million).

Mali’s junta has in recent months ramped up efforts to renegotiate existing mining contracts with foreign companies including B2Gold Corp., Allied Gold Corp. and AngloGold Ashanti Plc. Last month it briefly jailed four employees of Barrick Gold Corp. and threatened to take back a concession to a mine.

Resolute’s employees are being treated well and the company is in “regular communication” with all three, the Perth-based miner said Monday. Mali’s mining ministry has not commented on the arrest. The Australian government did not immediately respond to a request for comment.

Resolute has ramped up output at its Syama mine in the nation’s southeast and a second phase of the mine is expected to be in operation in 2025. The government holds a 20% stake in the project, which produces around 2.4 million tons of ore a year, according to Resolute’s website.

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“Resolute has followed all official processes with respect to its affairs and has provided the authorities with detailed responses to all the claims made,” the company said. “While Resolute is working toward a settlement with the Government of Mali to help secure the long-term future of the Syama Gold Mine, the upmost priority remains the safety and wellbeing of its employees.”

--With assistance from Paul-Alain Hunt, Katarina H?ije and William Clowes.

(Updates share price in third paragraph)

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