The RCMP are investigating an incident of labour friction at the strike-bound Voisey's Bay nickel mine in Labrador, amid an ongoing walkout and an NDP call to outlaw replacement workers.

Unionized mine workers walked off the job Wednesday, shutting down the mine's mill and posing a threat to production as a strike involving about 120 support staff workers continues in its sixth week.

(CBC)(CBC)

RCMP officers are probing a confrontation on Tuesday night in which a replacement worker employed by Ushitau Maintenance barred several direct Voisey's Bay Nickel employees inside a shipping container.

The company flew the replacement worker off the site soon after, but unionized workers wanted more workers removed.

Darren Cove, president of the United Steelworkers local — which is representing both the striking support-staff employees and the Voisey's Bay Nickel workers who walked out — said the dispute started when one of the regular workers used a camera phone to take pictures of the replacement worker.

That worker, Cove said, became upset and barricaded the others. A supervisor had to step in to free the five workers.

Cove said staff do not feel safe amid tensions that have been simmering for weeks.

Replacement workers were brought in after staff employed by Ushitau and Torngait Services took separate strike votes in mid-April.

Ushitau managers admit the employee acted inappropriately.

Lorraine Michael, leader of the New Democratic party in Newfoundland and Labrador, said the provincial government has a legislative role to play.

"I think the kind of incidents that have been reported are the result of having replacement workers," Michael told reporters Thursday.

Work continues in mine

"Replacement workers have always led to violence, if you look anywhere across Canada, and if we want to end the violence, then you have to stop the replacement workers."

Although the mill has been shut down by the walkout, work is continuing in other areas of the mine.

Voisey's Bay Nickel said the shutdown will not affect the arrival this weekend of a ship that is scheduled to take away nickel concentrate for processing.

Unionized workers at the Voisey's Bay mine waged a 10-week strike in 2006, which ended with a richer benefits package.

Among other issues, the support workers — who handle duties ranging from housekeeping to airstrip maintenance — are seeking parity in quarterly bonuses paid to direct employees of the mine.