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Image courtesy of Alberta Energy Regulator.

Alberta regulators have stopped work at Canada Natural Resources’ Wolf Lake oil sands project after oil products leaked into an underground aquifer.

A benzene leak was detected by Canada Natural Resources on October 29 after a thermal well casing broke.

Samples taken from a test well near the site indicated elevated levels of benzene.

Regulators said BTEX, a mixture that includes benzene, toluene, xylene and ethylbenze, was detected in the samples.

The incident was officially reported by the Alberta Energy Regulator (AER) on December 19.

The site is located near Cold Water, Canada and is adjacent to Canada Natural Resources’ Primrose site.

The size of the discharge has not been disclosed.

The company said the leak occurred about nine miles away from the nearest private use water well.

Alberta-based Canada Natural Resources is working with the AER to investigate the incident.

Operations at the site will be suspended until the cause of the leak is determined.

An AER spokesman told the Edmonton Journal the BTEX mixture could possibly be naturally occurring.

In 2013, the AER restricted steam injection and enhanced monitoring at the Wolf Lake and Primrose sites after four leaks were discovered at Primrose.