Australian mining services provider Perenti Global Ltd said 19 employees were among the more than three dozen people killed in a ambush of a convoy ferrying workers near a Canadian-owned mine in Burkina Faso.
Gold miner Semafo Inc said five of its buses with a military escort came under fire on Wednesday on the road to its Boungou mine in the eastern region of Est.
The attack killed at least 37 and wounded 60, local authorities said.
Perenti said 20 employees were hospitalised after the attack.
Perenti employees killed or wounded worked for its African Mining Services unit, contracted by Semafo at Boungou mine.
The company said numbers were yet to be officially confirmed. It added work at Boungou mine was suspended and it was planning to send staff back home and assess the impact of the suspension on its earnings guidance for the 2020 financial year.
In a separate statement, Geodrill Ltd said two employees were killed in the incident.
It remains unclear how many people were in the convoy, what their nationalities were or how many are missing. Two security sources said dozens may still be unaccounted for.