MINNEAPOLIS (AP) — U.S. Steel plans to idle part of its Minntac plant in Mountain Iron, resulting in layoffs for about 680 workers.

It's the latest symptom of the downturn in the American steel and iron mining industry. U.S. Steel cites high steel imports, dumping and low steel prices.

U.S. Steel spokeswoman Courtney Boone says the layoffs at Minntac are temporary, but the company can't speculate how long they'll last.

Earlier this month U.S. Steel said it wouldy idle its Keetac plant in Keewatin effective May 13, idling 412 workers. And Magnetation announced in February that it was shutting down its Keewatin plant, resulting in about 20 job losses.