Protestors in Peru’s Arequipa region have clashed with police while demonstrating against US-based Southern Copper’s $1.4bn Tia Maria mine project.

Local police fired tear gas and rubber bullets at the 600 to 700 people, as the ‘indefinite strike’ threatened to delay the project, Reuters reported.

Southern Copper is located in the south of Peru, in the Moquegua region, which is said to have the largest copper reserves in the country with estimates of 641 million tonnes of ore grading at 0.39% copper.

"Local police fired tear gas and rubber bullets at the 600 to 700 people."

Southern Copper secured government approval for the mine’s environmental plan earlier this year and hopes to receive a building permit by the end of March.

The company’s first environmental plan had been rejected due to various protests in 2011 that were said to have turned deadly. Those opposed to the Tia Maria mine development claim that the project may pollute agricultural valleys.

Southern Copper, which is controlled by Grupo Mexico, said it plans to start work on the mine upon receiving the construction permit.

Securing approval is considered a formality in Peru after obtaining environmental plan approval for a project, Reuters said.

Tia Maria copper mine project received its Environmental Impact Assessment (EIA) study approval on 1 August 2014.

Southern Copper hired Peru’s engineering and consulting firm Geoservice Ingeniería to carry out the EIA studies.