Police and copper workers have clashed during a strike over pay in Chile, the world's biggest copper producer.
The effect on copper production is unclear
Two officers were injured and 42 people arrested in the city of Rancagua.
Some 28,000 contract workers at Chile's state-owned copper company Codelco are said to be taking part in the nationwide walk-out.
The strike comes as copper prices are at record levels on the world market and the workers are calling for those prices to be reflected in a $960 bonus.
The strikers are also demanding better employment terms - they say union workers, who number around 14,000, receive higher salaries.
The government has insisted it will not give the workers a bonus, but has said it is prepared to discuss improvements in labour conditions.
Police said strikers in Rancagua, south of the capital, had tried to prevent regular employees from reaching the El Teniente mine, the world's largest underground copper mine.
Six demonstrators were arrested when they tried to hijack a bus, police said.
A group of about 200 workers then went to the police station to demand their release and violence erupted.
A representative of the contract workers called on the government to curb police action.
"We just want to hold a peaceful demonstration," Danilo Jorquera, co-ordinator for the contract workers, said.
The strike comes less than two weeks before Chileans go to the polls to choose their president in a run-off vote.
It is not clear what effect the walk-out might have on copper production.