A violent protest on March 24 by contract workers halted operations at Anglo American’s Los Bronces copper mine in Chile.

Contract workers launched the protest that included tires being set on fire and damage to installations at the mine site over what they say are layoff threats and Anglo American’s refusal to negotiate a series of demands.

Reuters reported that it is unclear how long the labor action could last and that a union leader said there was interest in reaching agreement with the company to resolve the dispute.

Anglo American said it had been forced to halt operations because of the protests.

"The process of halting the mineral-processing plants has started, and once finished the evacuation of workers will begin, in so far as we have safety guarantees for the internal and external roads," Anglo said in a statement, adding it had asked for authorities' help.

The protests highlight growing tensions with contract workers, who are usually paid less than their staff counterparts for similar work, at a time when Chile's mining boom is slowing.

"The issue with contract workers explodes once in a while," Juan Carlos Guajardo, the head of mining think tank CESCO told Reuters.

He stressed, however, "the violence is very concerning. It's generating more and more complications in Chilean mining ... I think we could see more cases like these."

Chile has been hit by massive mining strikes in the past, especially when copper prices were higher and workers were seeking a bigger share of the pie.

The company's Chilean Twitter account posted a picture of hooded men wheeling gigantic tires and another one showing black smoke billowing from a fire that appeared to be engulfing a row of tires.

Anglo owns 50.1 percent of the deposit. Chilean state miner Codelco and Japanese trading houses Mitsui & Co and Mitsubishi Corp. also have stakes in the complex.

Anglo American's other mines in Chile are operating normally, the company added.