Codelco, the world's No. 1 copper producer, said it was still investigating the cause of the accident at Chuquicamata that left two workers dead when the vehicle they were driving collided with a giant mining truck.
Chile's mining regulator said operations at Freeport's El Abra partially resumed on Wednesday.
Activities were halted on Tuesday after a worker died following an accident at its acid unloading terminal.
Century-old Chuquicamata produced 309,000 tonnes of copper in 2015, while El Abra, which is 51 percent owned by Freeport and 49 percent owned by Codelco, produced around 147,000 tonnes.