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Unidentified assailants attacked a convoy transporting workers of Canadian gold producer Semafo Inc. in Burkina Faso, killing at least 37 people, the government said.

The deaths come as West African governments battle a widening insurgency by Islamist militants and at a time when gold producers and prospectors are pouring money into the region as prices rally.

Five buses transporting employees, contractors and suppliers were ambushed Wednesday on a road between the eastern town of Fada and Semafo’s Boungou mine, the Montreal-based company said in a statement. The incident happened about 40 kilometers (25 miles) away from the Boungou site and the mine’s operations are unaffected, it said.

The convoy was hit by a “complex attack,” in which 60 people were injured, Burkina Faso’s government said in a statement. The state will provide further details later on Thursday, while Semafo said it will issue an update “when complete details are known.”

Semafo’s stock closed 11% lower at C$3.49 in Toronto, the most since April 2017. Shares in Australia’s Perenti Global Ltd. dropped by a similar margin after it said members of its workforce in Burkina Faso were involved in the incident.

The attack is the third related to Semafo in the past 15 months, after two incidents last year left at least seven people dead.

No one claimed responsibility for the assault, but Islamist insurgents and militants linked to al-Qaeda and the Islamic State have carried out several attacks on security forces and civilians in West Africa in the past five years, killing almost 700 people.

(Updates with drop in Perenti share price in fifth paragraph)

--With assistance from Victoria Batchelor.

To contact the reporters on this story: Simon Gongo in Ouagadougou at sgongo@bloomberg.net;Katarina Hoije in Abidjan at khoije@bloomberg.net

To contact the editors responsible for this story: Andre Janse van Vuuren at ajansevanvuu@bloomberg.net, Ekow Dontoh

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