VANCOUVER - For the sixth time in nine months, and the second time in three days, a bomb has exploded near EnCana's natural gas pipeline in northeastern British Columbia.

The blast early Saturday morning took place less than a kilometre from where EnCana workers were trying to cap a gas well damaged in an explosion Thursday.

"Our crews were at the wellhead site, where they were working to stop the gas leak," EnCana spokeswoman Rhona DelFrari said from Calgary.

"Around 2:30 in the morning they heard a loud bang, so they immediately went to the spot where they thought it was and that's where they discovered the explosion at the pipeline."

The Mounties are labelling the bombings as domestic terrorism and have flown in a unit of its Integrated National Security Enforcement Team to investigate.

RCMP spokesman Cpl. Dan Moskaluk said the EnCana crew, as well as a nearby resident, reported the explosion.

The blast caused a brief leak of potentially toxic sour gas but the pipeline's control system sensed the drop in pressure and triggered emergency shutdown valves to isolate that portion of the line.

It's not clear whether the EnCana repair crew was downwind of the leak but Moskaluk said no one was hurt.

Some nearby residents evacuated their homes when they heard the blast, said DelFrari, but it was unnecessary.

The small amount of leaked sour gas dissipated instantly, she said, and tests of the air showed no signs of hydrogen sulphide, which can kill in small quantities.

"So there was no risk to the public," said DelFrari.

It's the sixth bombing against EnCana (TSX:ECA) gas-transmission facilities since October.

The bombings have all taken place along a 15-to-20-kilometre stretch of the pipeline near Pouce Coupe, just south of Dawson Creek on the B.C.-Alberta border about 1,050 kilometres northeast of Vancouver.

The string of unsolved bombings has left Pouce Coupe, which has less than 800 residents, edgy and suspicious.

"This is an attack on the entire community now," said DelFrari. "This isn't just an attack on EnCana as a corporation. This person is putting everyone's lives in risk right now."

Police suspect the bomber is someone who has a grudge against EnCana and who perhaps lives in the area.

The attacks began with three bombings shortly after a letter was sent to a Dawson Creek newspaper and to EnCana. It labelled oil and gas companies terrorists and demanded EnCana stop natural gas development in the area.

There was another explosion in January, then none until this week.

Most have targeted wells or pipelines carrying sour gas.

Moskaluk said though no one has been hurt yet, the bombings have created stress in Pouce Coupe, as well as nearby Dawson Creek, which depends economically on energy development.

"Many have been questioned, many have been brought in for interviews," he said.

"They're all looking at one another. You can imagine how that's eating away at people."

Moskaluk said police won't be releasing information on the type of explosives used or the bombs' construction. He could not say if the latest bomb had been planted before or after Thursday's blast.

He said police hope this sixth attack will trigger some tips to help them catch the bomber.

I think if somebody comes forward then I think there's a little bit of strength in numbers," said Moskaluk.

EnCana has offered a $500,000 reward for information and set up a special phone line for the bomber to call them but so far it hasn't rung.

Meanwhile, EnCana is maintaining bolstered, 24-hour security along the pipeline. But DelFrari admitted there's no way to ensure the bomber doesn't strike again.

"Let's face it, it's hard to patrol hundreds of kilometres of pipeline and we have about 150 wells in the Dawson area," she said.