SANTIAGO (Reuters) -Two recent accidents involving autonomous trucks are raising safety concerns, a workers' union at BHP's Escondida mine in Chile, the world's largest copper mine, said in a statement on Wednesday.

The union, which has often been critical of BHP and has staged strikes as part of contract negotiations, said that on August 25 an autonomous truck collided with shovel machinery and the week before, another truck overturned.

It did not report any injuries.

Despite that, the head of the Union Patricio Tapia told Reuters that while workers don't operate the vehicles, they perform other tasks in the area like maintaining roads.

In a statement, BHP said it has trained more than 4,800 workers in its automation process and has "totally eliminated" having people exposed when material is moved in the open pit.

BHP said that one of the incidents involving the autonomous trucks happened in March.

"In the other incident, that involved a mechanical shovel with an autonomous truck, there were no exposed people and it is still under internal investigation," the statement said.

The company in July said it had fully implemented autonomous operations for 33 trucks and eight drills at the mine's Escondida Norte unit, completing a five-year rollout.

"Less than a month since the announcement, the reality is revealing a huge risk to the safety of workers," the statement said.

Escondida produced 1.28 million tons of copper last year.

(Reporting by Fabian Andres Cambero; writing by Natalia Siniawski, Paolo Laudani and Alexander Villegas; Editing by Daina Beth Solomon and Alistair Bell)