Police in Canada suspect sabotage was the cause of the second explosion on a natural gas pipeline within a week.
The blast was discovered on Thursday morning near Dawson Creek in British Columbia.
In a statement, the Royal Canadian Mounted Police said it was the second such incident this week in the same area and it appeared the two events were related.
The explosion did not rupture the pipeline, although there was a small leak.
The pipeline is owned by EnCana, North America's biggest independent oil company, based in Calgary.
An earlier blast, about 50km along the same pipeline on Saturday, left a crater but caused no damage.