Investors in Eritrea's mines risk complicity in gross human rights violations unless they take effective steps to ensure that no forced labour is used in connection with their operations, Human Rights Watch warned on Tuesday.In a report examining the operations of Nevsun Resources, Human Rights Watch said it found that the small Canadian company was obliged to used a state-owned contractor, Segen Construction Company, to build some of the infrastructure around the mine site.Segen has a long track record of allegedly deploying forced labour in connection with its projects, according to Human Rights Watch, which interviewed four Eritreans who worked at the Bisha project, Eritrea's first and so far only operational mine. It began gold production in 2011 and produced $614m worth of ore in its first year. The project is majority owned and operated by Nevsun Resources.The Eritreans interviewed by Human Rights Watch worked at Bisha during its initial construction phase. Some said Segen deployed them as conscript labourers, describing "terrible living conditions and forced labour at paltry wages". One former conscript said he was arrested and imprisoned for several months after leaving the work site to attend a relative's funeral.Under the "national service" programme, Eritreans are conscripted; most are sent to the military, but others are made to work for state-owned companies. Some of those companies are construction firms that the government pressures international companies to use as contractors, said the report."If mining companies are going to work in Eritrea, they need to make absolutely sure that their operations don't rely on forced labour," said Chris Albin-Lackey, business and human rights senior researcher at Human Rights Watch. "If they can't prevent this, they shouldn't move forward at all."The group said mining firms wanting to invest in Eritrea should refuse to work with any contractor implicated in the use of forced labour, and insist on the right to investigate any and all allegations of abuse connected to their operations.Nevsun said it became aware of allegations that Segen might be employing conscripts in early 2009, within a few months of the start of mine construction by its subsidiary, Bisha Share Mining Company (BMSC).Nevsun added: "Unfortunately, at the time, BMSC's national service discharge document inspection procedures did not apply to subcontractors. In response to the allegations BMSC acted quickly by immediately extending its procedures to include subcontractors and by obtaining a written guarantee from Segen that it would not use conscripts at Bisha."