TORONTO: Two workers at First Nickel Inc’s Lockerby Mine have died in an accident underground at the Sudbury, Ontario operation, the company said on Tuesday, bringing the total to six of those killed in area mines in the past three years.

First Nickel said both workers, Marc Methe, 34, and Norm Bissaillon, 49, were drillers employed by Taurus Drilling Services. All underground work at the northern Ontario mine has been suspended.

The small Canadian mining and exploration company said seismic activity preceded a “fall of material”, and was believed to have played a role in the accident.

Neither First Nickel nor Taurus Drilling could be reached for comment. Ontario, Canada’s most populous province is in the midst of a mine safety review, looking at the effectiveness of health and safety rules, enforcement and prevention in the industry.

The review came after more than a year of lobbying by families and friends of two men killed in 2011 at another Sudbury mine, owned by Vale SA, as well labor leaders and other allies.

The Brazilian miner was hit with a record C$1.05 million ($964,000) fine for that incident last year. It pleaded guilty to three counts of violating the province’s workplace safety law.

Last month one worker was killed and another was injured at Vale’s Copper Cliff smelter in Sudbury. Another worker was killed at Vale’s Coleman mine in Sudbury in January 2012.