Coal miners in Zambia killed one Chinese manager and injured another during a riot Saturday.

The miners were on strike at the Chinese-owned Collum coal mine in Sinazongwe in protest of delays in raising the minimum wage. They were incensed because their wages were below a new minimum of $220 per month paid to shop workers, according to BBC News.

Wu Shengzai, 50, was killed after being struck by a mine cart that workers pushed toward him as he ran away down a mine shaft, police said.

The latest incident at the Collum coal mine follows one there last year, when two Chinese managers fired upon protesting workers, injuring at least 11. The Zambian government ultimately dropped charges of attempted murder against the two managers.

China has invested more than $400 million in Zambia, which is rich in coal and copper deposits. Copper mining alone accounts for nearly three-quarters of the country's exports.

However, Human Rights Watch has criticized conditions at Chinese-owned copper mines in Zambia, claiming there are "persistent abuses in Chinese-run mines, including poor health and safety conditions, regular 12-hour and even 18-hour shifts involving arduous labor, and anti-union activities, all in violation of Zambia's national laws or international labor standards."