Five thousand tonnes of rock fell from the edge of the open pit at Diavik Diamond Mine last week but employees got out 10 hours before the rockslide started.
Two alarm systems alerted workers that the rock was unstable.
"Both systems worked, nobody was injured," said Corey McLachlan, a spokesperson for the mine.
"I think there is a recognition that rock slides will happen periodically. So it's very comforting to know that our systems work and give us lots of advance notice and we're confident and believe in zero harm — we don't want to see anyone injured. This is a great example of systems that we have in place to ensure that we have a safe workplace."
Employees at the mine didn't resume work in the pit for seven days after the rockslide.
McLachlan said they're clearing the fallen rocks, and have added heavy-duty mesh at the opening of the pit.
This week, work resumed during daylight hours. McLachlan said the mine is completing more geotechnical tests before going back to 24-hour operations.