Cuba has sentenced a dozen people to prison for corruption, including high-ranking government officials and employees of a jointly run Cuban-Canadian nickel operation.

A bulletin published in Communist Party newspaper Granma on Tuesday announced the prison terms ranging from four to 12 years.

Those convicted include three former vice ministers of the Ministry of Basic Industry, which oversees nickel mining.

Also sentenced were the director and other employees of state-run Cubaniquel and workers from Empresa Moa Nickel SA. The latter is jointly held by Cuba and Canadian mining company Sherritt International Corp.

The notice in Granma says the case involved the contracting and execution of the expansion of the Moa nickel mine’s Pedro Soto Alba processing plant.

Nickel production is one of Cuba’s main sources of foreign income.