SANTIAGO, June 25 (Xinhua) -- At least six miners were killed and 34 others injured when a bus transporting the workers overturned in northern Chile, authorities said on Tuesday.

And two of the injured were in critical condition, said the National Emergency Office of the Interior Ministry.

The accident happened Monday night on Ruta A-65 which connects the city of Iquique, some 1,785 km north of the capital of Santiago, with the Collahuasi mines.

Following the accident, police closed the road and an investigation was underway to determine the cause of the tragedy, which is believed to be brake failure.

Efrain Lillo, superintendent of local fire department, told reporters that it was "a major accident, the bus overturned, we had people trapped inside the bus who were rescued by firefighters."

Collahuasi is a mining company dedicated to the extraction and production of copper concentrate and cathodes, and molybdenum concentrate.