The RCMP says it's "very concerned" about another threatening letter sent to a Dawson Creek newspaper purportedly by a pipeline bomber in northeastern B.C.

The letter warns attacks will "get a lot worse" if EnCana, the company that produces and ships natural gas in the area, doesn't start pulling out within three months.

The Dawson Creek Daily News says the two-page handwritten letter, which it received on Wednesday, promises a "summer vacation" free of attacks. But the letter warns that will change unless EnCana announces a pullout plan by the fall.

"The contents of the letter are of very grave concern to our investigators," RCMP spokesperson Sgt. Tim Shields told reporters.

The RCMP has anti-terrorism officers on the case, and is appealing for more information from the public.

"We know it is very likely that there is more than one person who knows who's responsible for these series of bombings," Shields said. "There's a potential for loss of life here."

The letter doesn't specify the exact area EnCana must leave, but it mentions a plant in the Kelly Lake area.

Last October several media outlets received an initial anonymous letter. It also warned EnCana to stop drilling and leave the area. It complained about the production of "crazy" natural gas.

Critics claim the production of natural gas emits "sour gas" which can be harmful to livestock.

Since then there have been six mysterious explosions targeting EnCana projects in the region.

The most recent blasts took place July 1 and 4 near the community of Pouce Coupe, B.C., just south of Dawson Creek, which is about 575 kilometres northwest of Edmonton.

The RCMP has called the bombings "domestic terrorism."