We've been telling you about a pipeline spill discovered near Belfield last week, where nearly 200,000 gallons of crude oil leaked into Ash Coulee Creek, and we've now discovered the company responsible wasn't even aware that it happened at the time.

The Department of Health says the spill was discovered by a landowner last Monday.

True Cos. which owns the pipeline says that the spill was contained after 176,000 gallons of crude oil had leaked from the pipe. Cleanup efforts are underway and more than 36,000 gallons have already been recovered.

Wendy Owen, a spokesperson for the company, says the sensors which detect leaks may have not worked properly.

“The line did have a monitoring system on it and for whatever reason the leak was not detected. It's possible that because of the intermittent flow on that particular line, it was masked - the leak was masked,” says Owen.

Owen says the crude oil has not contaminated anyone's drinking water supply.