​Police say they are investigating significant damage to an oilfield pipeline under construction in the Hythe area in northwest Alberta.

Beaverlodge RCMP received a report on Sunday about mischief at a pipeline site north of Hythe, Alta.

Damage to the pipeline is estimated at $500,000 to $700,000, police say.

RCMP in Grande Prairie told CBC News that vandals used construction equipment at the site to dig up a portion of the pipeline, which will now have to be replaced.

The investigation continues.

The Alberta Energy Regulator said it was notified of the vandalism by the company, Paramount Resources.

The pipeline was still under construction, so there was no spill, said AER spokesman Ryan Bartlett.

Darrel Purdy, a spokesman for Paramount Resources, said no security personnel were on site at the time the damage was done.

Such measures wouldn't be a common industry standard, he said.

Construction equipment on the site has now been secured, Purdy said, and a security detail is in place.

Transmission pipelines generally have 24-hour security on site, but that can be costly and labour intensive, said Patrick Smyth, vice-president of safety and engineering with the Canadian Energy Pipeline Association. The organization represents companies that operate 119,000 kilometres of oil and gas transmission pipelines in Canada.

"You could have security personnel out there driving," Smyth said. "But if there is an individual, or individuals, out there that want to cause harm, they can could get in there and they could perform nasty activities to the pipeline while security is at the other end."

Smyth said in this case the pipeline was in a remote area, and few people would have even known it was there.

"I think the lesson out of this one is, there is no construction site that is off base for those who might want to cause harm to Canada's critical energy infrastructure.

"Even though it seems out of sight, and out of mind, those who want to perform damage, they're going to get in there. So it just means the onus is back on the company to ensure that they have a very comprehensive security plan in place."

This is not the first time that oil company infrastructure in that part of Alberta has been targeted by vandals.

During the 1990s, a landowner in the area engaged in a lengthy battle with oil companies in the Hythe area.

Wiebo Ludwig was eventually convicted on five charges related to bombings and vandalism of oil and gas wells. He served 19 months in jail.

In January 2010, RCMP officers searched the Ludwig family's 325-hectare farm, looking for evidence related to six Encana gas pipeline bombings in B.C. between October 2008 and July 2009.

Ludwig was arrested but released the next day, and was never charged. He died of cancer in 2012.

Hythe is about 60 km northwest of Grande Prairie.