RIO DE JANEIRO, Aug. 27 (Xinhua) -- About 12 percent of all charcoal bunkers in Brazil's Amazon rainforest region still uses slave workforce, said a human rights monitoring group Monday.

The worst working conditions were found in Para, northwest Brazil, the Citizen Coal Institute (ICC) said, adding that inhuman working conditions were also tracked in the states of Tocantins, Maranhao and Piaui.

The ICC is a monitoring organization funded by a group of 14 pig iron producers that operate in Carajas located in the state of Para. The iron producers export about 6 million tons of pig iron per year.

The Amazon charcoal is used as raw material for the production of pig iron in the region. According to the ICC, a total of 1,500 charcoal bunkers were installed in order to meet the demand.

In September 2004, Brazil's Ministry of Labor signed an agreement with pig iron producers aimed at fighting slavery in the region and "huge progress has been achieved," said the ICC.

Only 2 to 5 percent of the charcoal bunkers in Para state met the standard of the agreement at the beginning, according to the ICC.