Chinese-owned iron miner Shougang Hierro Peru SAA (SHPC1.VL) said Thursday that contract workers had blocked access to its mine site from early in the morning.

In a letter to the Peruvian regulatory agency, the company said that contract service workers blocked a highway, stopping access by workers and affecting production.

"We have become aware that persons from a service company are carrying out unacceptable violent acts that are tied to administrative demands made by their employers," Shougang said.

The company has been hit by a number of labor dispute stoppages in recent years.

The mine is located at San Juan de Marcona, 525 kilometres southeast of Lima.

On its Web site, the company says that "The actual total production capacity is 4,500,000 to 5,000,000 tons per year."

Shougang Hierro Peru, a unit of China's Shougang Group (SHGG.YY), has owned Peru's only iron ore mine since 1993.