Union president Darrin Kruger said the incident happened on Sunday.

While Agrium said the potash mine, which can generate 7,000 tonnes per day, has reopened, Kruger said production remains shut.

Kruger said the worker is recovering in hospital after surgery.

"His injuries are not life-threatening, but he's got a long road to recovery," Kruger said. "Full recovery is unknown at this time."

He declined to comment on the specifics of the injuries or how they occurred, saying the worker's family requested privacy.

Kruger said a provincial workplace safety body is investigating, and it might take days for production to resume.

An Agrium spokesman confirmed the incident and said the company is also investigating.

(Reporting by Ethan Lou in Toronto; Editing by Chizu Nomiyama)