Canada-based uranium company Cameco has restricted underground mining activities at the Rabbit Lake operation in northern Saskatchewan after discovering a fall of rock in a tunnel when it reopened an inactive area of its Eagle Point mine.
Currently, 600 Cameco employees and contractors are working at Rabbit Lake.
Following the incident, no groundwater inflow has taken place at the mine's affected area.
Cameco evacuated 40 non-essential personnel from the mine and activities as a precautionary measure.
The company said no injuries were reported and there was no effect on the environment. It is in the process of evaluating the affected area.
Cameco also suspended production mining at Eagle Point temporarily and completed assessment.
The Rabbit Lake mill will continue to operate as usual.
The operation will process ore that was mined previously and transported to the surface and is expected to meet its production target of 3.9 million pounds of uranium concentrate in 2015.
Cameco informed the Canadian Nuclear Safety Commission and Saskatchewan Mines Inspector about the incident.
Rabbit Lake uranium milling facility is located about 800km north of Saskatoon, Saskatchewan, on the north-east edge of the uranium rich Athabasca Basin.
Production at Rabbit Lake deposit started in 1975.