VANCOUVER - The RCMP has identified "persons of interest" in connection with four gas pipeline bombings in northeastern British Columbia as the company being targeted offered a $500,000 reward Tuesday.

However, those people and others are not co-operating with the police investigation, RCMP Sgt. Tim Shields said.

"And to those people, we are asking that they do the right thing," Shields said. "They know who they are because we've spoken to them."

Shields made the comments at a news conference in which EnCana Corp. (TSX:ECA), one of Canada's largest energy companies, offered the reward for information directly leading to the arrest and prosecution in the recent bombings of its facilities in the gas-rich region.

There have been four bombing attacks on EnCana facilities near Dawson Creek since October.

The latest incident was discovered last week, when a metering shed near the community of Tomslake was damaged by a blast. The first three explosions last October involved pipelines or wellheads carrying sour gas, which contains toxic hydrogen sulphide.

Nobody has been injured but police have warned that the last blast was only about 250 metres from a residence.

The RCMP is making an appeal to family and friends of the "persons of interest" and asking them to come to police with their suspicions, Shields told a packed news conference at RCMP headquarters in Vancouver.

He refused to elaborate on the degree of resistance investigators have met with, but said "they are being less than co-operative."

Police have theories about why they are not co-operating but Shields again refused to elaborate.

With the most recent attack so close to a home, EnCana executive Mike Graham said they feel extremely fortunate that no one has been seriously hurt so far.

"But if the attacks continue there is a serious risk of injuries or even death," Graham said at the news conference.

He said the reward may not be for only one tip, but could be paid out in smaller increments depending on the quality of the information.

"After consulting with the RCMP and the Crown assigned to the prosecution, EnCana will determine the monetary value, if any, of the information provided to the investigation."

Mounties hit a dead end after identifying and ruling out eight people spotted on video surveillance in a store with a postal outlet on the same day a threatening letter was mailed.

The letter was sent to local media and EnCana, calling oil and gas companies, and EnCana in particular, "terrorists" and demanding the company stop natural gas operations in northeastern B.C.

EnCana, a major natural gas producer and oilsands operator, announced in December that it had cut its cash-flow expectations and announced a "conservative, prudent and flexible" 2009 capital budget of about US$6.1 billion, down 13 per cent from $7 billion this year.

EnCana is the major play in the oil and gas sector in northeastern B.C. There are more than 4,000 producing oil and gas wells in British Columbia, all in that area of the province.

The industry has seen massive growth since the mid-90s, with provincial revenues jumping from $370 million in 1996 to $2.5 billion in 2006 -- mostly related to natural gas projects.