UPDATE 1-Canada police ask for public help in bomb probe

(Updates with police news conference)

By Allan Dowd

VANCOUVER, British Columbia, Dec 3 (Reuters) - It is still not known if a single person or a group of people is behind three October bombings of natural gas facilities in Western Canada, police said on Wednesday.

"It could be one person acting alone. It could be somebody acting within a small group," Royal Canadian Mounted Police Sgt. Tim Shields said as investigators renewed their plea for the public's help.

Police have identified several "persons of interest" in the probe, but acknowledge some of them are refusing to co-operate. "They know who they are," Shields told reporters in Dawson Creek, British Columbia.

Police believe the saboteur, or saboteurs, lives in the same area of northeastern British Columbia where the three attacks occurred, and believe the motive is a grievance against pipeline owner EnCana Corp (ECA.TO).

Two pipelines and a gas wellhead were damaged in the attacks in October. There have been no injuries in the incidents, but two of the explosions caused small leaks.

Investigators released copies of an angry letter believed linked to the bombings that was mailed to local media and EnCana shortly before the first incident.

They also released photographs of eight people who mailed letters from the same drugstore in Dawson Creek that the suspect note was mailed from on Oct. 7.

The eight were not identified as potential suspects, Shields said police released pictures of them because they do not know their names and some may not know that investigators are interested in talking to them.

University of Alberta sociology researcher Paul Joosse, who has studied radical environmentalists, agrees with the police that the attacker is probably a local resident rather than part of a larger outside group.

But Joosse says one reason police may be having difficulty getting all residents to co-operate is because there is sympathy for the bomber's motives, even if the people disagree with the tactics.

The letter writer expressed anger at the production of "sour gas", natural gas that contains toxic hydrogen sulfide, which is removed at a processing plant near Tomslake, British Columbia, before the gas is shipped to market.

"We will not negotiate with terrorists which you are as you keep on endangering our families with crazy expansion of crazy gas wells in our home lands," read the letter, which demanded EnCana and other producers stop operations and leave.

EnCana also released a statement on Wednesday saying it does not believe the attacks were intended to to kill anyone, but it warned that could happen by accident if the incidents continue.

There were no attacks in November and security at energy facilities has been increased. The RCMP investigation includes members of the country's national anti-terrorism squad.

The RCMP has taken the unusual step of launching a dedicated website, www.dawsoncreekbombings.com, with information they hope will generate tips on who is responsible for the attacks. (Reporting Allan Dowd, editing by Rob Wilson)