The Alberta Energy Regulator is investigating another leak from a Canadian Natural Resources bitumen well near Cold Lake. 27,000 liters of crude bitumen were released underground on Jan. 3 at the company's troubled Primrose field.

But agency said the leak has been stopped. The release has been definitively attributed to a failed well casing, setting this leak apart from an earlier one in the same field last summer that also remains under investigation. In that leak, more than a million liters of bitumen has so far seeped to the surface.

The spill continues, although cold weather has slowed the amount to almost nothing. The company said, leak was also due to a well failure. The regulator is investigating whether the bitumen escaped through cracks in the rock above the deposit and was driven to the surface by high-pressure steam pumped underground to soften it before being extracted.

The company has been ordered to reduce the pressure of the steam it uses. There's no indication when the regulator's report on that leak will be complete.