DAWSON CREEK, B.C. - The RCMP say a bomb was behind a leak at a gas well belonging to Calgary-based EnCana, one of the major players in northern British Columbia's rapidly expanding oil and gas industry.

It's the fifth time since last fall that the company's oil and gas operations have been targeted.

The Mounties said Thursday that the gas leak discovered on Canada Day at an EnCana sweet gas well south of Dawson Creek, not far from the B.C.-Alberta boundary, was caused by an explosion.

And while investigators hadn't yet been able to start an extensive forensic investigation of the scene, the force had already linked the attack to four others last October and January.

"Preliminary examinations of the natural gas leak at one of the EnCana natural gas pipeline sites at Pouce Coupe, B.C., confirm that the rupture was caused by an explosion," the RCMP said in a news release.

"This blast is considered the fifth in a series of criminally motivated acts that have occurred at EnCana sites."

The leak was discovered by an EnCana employee Wednesday morning at the sweet gas well near the village of Pouce Coupe. The worker was conducting a routine check when he noticed the damage to the wellhead, as well as a drop in pressure.

Investigators with the RCMP's Integrated National Security Enforcement Team were waiting for EnCana to seal off the leak before moving in to gather evidence.

The well is about three kilometres away from the nearest resident and EnCana said the leak doesn't pose a risk to the public.

Company spokeswoman Rhona DelFrari said crews were "really close" to stopping the leak by late Thursday afternoon and hoped to seal it by day's end.

"They're hoping that the gas leak will be stopped tonight," she said in an interview.

Last October, a hand-written letter was sent to local media in Dawson Creek and to EnCana, calling oil and gas companies, and EnCana in particular, "terrorists" and demanding the company stop natural gas operations in northeastern B.C.

There were three explosions later that month at EnCana pipelines or wellheads carrying sour gas, which contains toxic hydrogen sulphide. Two of those bombings caused leaks, one of which took about two days to stop.

Then, in January, an explosion destroyed a metering shed at a wellhead near the nearby community of Tomslake.

Investigators have said they believe the attacks are the work of someone with a grievance against EnCana, which says it has about 150 wells in the Dawson Creek area.

The RCMP have asked for public tips in the case, and EnCana is offering a $500,000 reward for information.

EnCana has also set up a dedicated telephone line for the bomber to call them and talk about their concerns, but DelFrari said so far no one has called.

While EnCana insists it has a good relationship with locals, many of whom have EnCana pipes or wellheads sitting on their properties, the bombings brought attention to animosity among residents concerned about noise, the environment and the dangers of living next to sour gas projects.

Pouce Coupe's mayor, Lyman Clark, said Thursday that the company has done a good job keeping an open dialogue with residents and addressing their concerns, but he admits some still aren't happy.

"I do hear rumblings about the noise and the dust -- when they're drilling, those things are quite noisy," said Clark.

"Yes, there is animosity to some degree. We try to listen to everybody's complaints and forward them to the gas company. ... We feel they (EnCana) are trying their best."

B.C. has more than 4,000 producing oil and gas wells, all in the northeastern part of the province, and the industry has grown quickly during the past decade.

In 1996, it was worth about $370 million in revenues to the province. By 2006, that figure had jumped to $2.5 billion, mostly related to natural gas projects.