RCMP Sgt. Tim Shields said the explosion on Friday appeared to have been deliberately detonated. (CBC)

Investigators with the RCMP's Integrated National Security Enforcement Team renewed their call for the public's help Saturday as they probed a third explosion targeting natural gas pipelines in northeastern B.C.

Crews from oil and gas giant EnCana Corp., whose pipelines have been the target of all three blasts, were still at the scene near Dawson Creek, B.C., at midday, trying to stop the flow of gas.

Police investigators have numerous leads, but continue to believe whoever was responsible for the explosion has extensive local knowledge and may be from the area, RCMP spokesman Sgt. Tim Shields told a news conference.

"When looking at when and where the attacks occurred, it is safe to say that the person or persons responsible knows how to locate the sites and has knowledge of the sites," Shields said.

"For a person to have this information, they would likely have to be from the immediate area or have spent significant time in the area."

The latest blast suggests the incidents are moving closer to populated areas, Shields added.

An EnCana spokesperson said the latest leak is small and does not pose a threat to the public. (CBC)

EnCana spokeswoman Rhona DelFrari said the current gas leak is small and there is no dangerous hydrogen sulphide leaking from the damaged area.

The first blast on Oct. 11 was beside a sour gas line about 50 kilometres east of Dawson Creek, B.C. The second occurred Oct. 16 along a pipeline off Highway 2, about half a kilometre from the Alberta boundary.

The third blast occurred Friday, about 12 kilometres northwest of Tomslake, B.C., near the Alberta border.

The natural gas from the wells contains just a trace of toxic hydrogen sulphide — 0.0005 to .001 per cent — but not enough to pose a health hazard, DelFrari said.

Many critics of sour gas development fear the gas, which can be fatal if too much is inhaled, poses a danger to people nearby.