Members of a union at Lundin Mining Corp.’s Chilean copper operation began a strike after a breakdown in wage negotiations that are being tracked by several other mines in the metal’s top-producing nation.

About 350 members of the Mina Union downed tools Thursday at the Candelaria mine. The company said that while it respects the right to strike, it condemned a group of people who blocked accesses and set tires alight. Other workers and contractors are keeping the mine running, it said.

While Candelaria produces far less copper than giant Chilean mines owned by BHP Group and Codelco, the collapse in talks underscores supply risks in a country that accounts for a quarter of global production. This quarter, mines with annual output of 2.8 million tons have labor negotiations that need to be settled, according to UBS analysts.

Candelaria management delivered a new offer in the last day of mediated talks on Tuesday, but the company didn’t request an extension to the mediation that would have allowed union leaders to present the proposal to members, the union said in a notice. In a previous notice, the union said members would vote on the offer.

“It was never our goal to reach these instances, but the intransigence of the company makes us take this path as a fundamental right to achieve benefits,” the union wrote.

In a statement Thursday, Candelaria said it remained “committed to responsible, peaceful and fair negotiations.” While the company expressed its respect for the right to strike, “it categorically rejects all actions that compromise the health and safety of all our own workers and contractors, as well as those of the communities.”

The mine is also engaged in wage negotiations with a second union, whose 548 members rejected a final offer in regular talks. Candelaria hasn’t indicated whether it will request mediation with the second union.

A similar process is under way at Escondida, the world’s biggest copper mine, with a union of supervisors scheduled to conclude an initial mediation period with owner BHP. Without an accord, the supervisors could begin a strike or the two sides could request another five days of mediation.

Escondida churned out 1.19 million tons last year, compared with Candelaria’s 111,400 tons, Chilean government data show.