Investigators from the Integrated National Security Enforcement Team renewed their call for the public's help Saturday as they continued to probe a third deliberate explosion targeting natural gas pipelines in northeastern B.C.

Crews from oil and gas giant EnCana, 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 whomever 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 is a concern because it suggests the incidents are moving closer to populated areas, Shields added.

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

The first blast on Oct. 11 was beside a sour gas line located 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.

Police Delays

Police were called to the scene more than 12 hours after the blast when workers heard the sound of leaking gas from a wellhead northwest of the small community of Tomslake.

Shields said police were concerned that a number of people heard the latest blast, but that none reported it.

"This often occurs when people think that somebody else will inform the authorities," he said. "We, of course, would rather have duplicate calls to ensure that we are aware of any potential situation.

"For investigators, and from a public safety standpoint, it's important for police to receive the information as soon as possible to contain the scene and potentially catch whomever is responsible for these acts."

DelFrari said the company is required to have emergency plans in place for its well sites.

"The plans tell us exactly when we have to alert the public if they could possibly be at risk," she said.

"In none of these cases was there ever any indication that the public was at risk, or that we actually needed to alert people, but we did it out of courtesy to some of the nearby residents."

The natural gas from the wells contains a fractional trace of toxic hydrogen sulphide -- 0.0005 to .0010 per cent, the company said -- but not enough to pose a health hazard.

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

Previous Incidents

The case has kindled memories of the vandalism that plagued Alberta's oilpatch in the 1990s.

There were more than 150 incidents at oil and natural gas facilities in northwestern Alberta between 1996 and 1998, ranging from shootings to nails found strewn along lease roads.

Alberta farmer Wiebo Ludwig, who blamed the energy industry and sour gas emissions for harming his land, livestock and family, was convicted of several charges related to oilpatch bombing and vandalism and spent nearly two years in prison.

Northeastern British Columbia has become a hotbed for the oil and gas industry in recent months. Several energy players have been flocking to the area in a bid to exploit the billions of cubic feet of natural gas trapped in the region's rock and sand.

The British Columbia government sold oil and gas rights totaling $151.8 million in October, bringing the year-to-date total to $2.17 billion, which is double last year's annual total.

EnCana is one of the largest players in the rapidly growing oil and gas industry in northeastern B.C.

Dragan Trajkov, an oil and gas analyst at Salman Partners in Calgary, said he believes the company may be being targeted because of its status as a major player in the industry.

"Whoever is targeting them probably thinks they will get more publicity out of the EnCana name," said Trajkov.