US law firm Bernstein Liebhard said the suit would deal with "misleading statements" made by the precious metals producer, which has had 21 fatalities on its operations so far in 2018.
Miners are urging the government to lift a six-year ban on large-scale projects in the Philippines after the state removed restrictions on smaller ventures.
OZ Minerals has announced that it has a relevant interest in Avanco of more than 90%, which means the company will now “compulsorily acquire” all of the remaining shares and acquire the fellow copper producer entirely.
The miner, which has set an exploration objective of adding one million gold equivalent ounces to Cerro Moro's mineral inventory, has hiked its exploration budget for 2018 to $11.2 million from $9 million.