The February 18 spill at a Chinese-owned mine in Zambia's northern copperbelt released 50 million litres (13 million gallons) of toxic waste into a tributary of one of the country's longest rivers, the Kafue, which was also polluted, environmental groups said.

"The US government has ordered the immediate withdrawal of all US government personnel from Kitwe and nearby areas affected by the Sino Metals mine tailings dam spill," the embassy said in a social media post.

"Newly available information reveals the extent of hazardous and carcinogenic substances -- including arsenic, cyanide, uranium, and other heavy metals -- as well as the immediate and long-term health threats that exposure to these contaminants pose as long as they remain in the environment," it said.

The post did not say how many people were affected by the order and the Zambian government did not immediately comment or release similar advice for its nationals.

The area, about 285 kilometres (180 miles) north of the capital Lusaka, is a major hub for Zambia's copper production, which is one the largest in the world and includes significant Chinese investment.

The acid spill occurred when a tailings dam, which is used to capture waste from the mining process, collapsed.

Media reports from the area soon after the disaster said that the pollution had travelled more than 100 kilometres from the dam, killing fish and livestock.