The Calgary-based company that owns the pipeline that spilled 4.5 million litres of crude oil in northern Alberta apologized Friday for its handling of communications about the incident.

Plains Midstream Canada has come in for criticism from a number of sources for its response to the spill as well as its communication about cleanup efforts.

"I apologize we have not had more direct communication," president David Duckett said at a briefing in Calgary.

"Our efforts to date have been focused on containing and mitigating the impact of the release. We will ensure there's open, honest and timely communication with all affected parties," he said.

On Thursday, Alberta Premier Ed Stelmach criticized the firm's communications with a nearby aboriginal group, the Lubicon Cree, and with the public in general.

"From what I gather, they can be doing a better job," he told reporters.

At the briefing Friday, the company said it asked earlier in the day for a meeting with Stelmach to brief the premier on its efforts, but had not yet received a reply.

Duckett also told journalists Plains now has 300 people working at the site to contain the spill, minimize its impact and begin cleanup efforts. It estimated the cleanup would take two to four months.

The company said the spill has killed seven beavers, seven ducks and one migratory bird.

2 crack detection tests done

The company, which bought the pipeline from Imperial Oil in 2008, also said it has ruled out corrosion as the cause of the rupture. It said that crack detection tests had been run on the pipeline as recently as January and April of this year.

Plains said the break has been repaired but it is awaiting regulatory approval to restart. Duckett described as "significant" the effects on oil companies which have not been able use the pipeline. It carried about 187,000 barrels a day last year.

Davis Sheremata of the Energy Resources Conservation Board said regulators have not completed their inspection and assessment of the pipeline.

He said the failed section has been cut away and removed to an Edmonton lab for testing, and that investigators still weren't sure what went wrong, why it happened or if the problem is systemic throughout the system. It could be days or longer before regulators are satisfied.

"The company is welcome to their opinion, but it is the regulator here who is going to decide what the problem is, how much of the pipeline it impacts, what has to be done to repair that, and when it has been done satisfactorily," Sheremata said.

"If it is a systemic problem, we are facing a continued shut-in until we are assured that it can be put back into operation safely and any necessary repairs or upgrades have been made.

"Until we are absolutely 100 per cent certain that the pipeline can be put back into operation safely, we will not allow it to be put back online."

The leak occurred about 100 kilometres northeast of Peace River, Alta. Google Maps

Reporters were told, when the break was first reported a week ago, that a few hundred barrels of oil had leaked.

But on Tuesday, Alberta's Energy Resources Conservation Board — the provincial energy regulator — reported 28,000 barrels had spilled, making it the largest Alberta pipeline discharge in 36 years.

Earlier media reports had said Stelmach was critical of Plains' cleanup efforts, saying that the firm would not be allowed to reopen its aging Rainbow pipeline until the spilled oil is properly cleaned up, repairs were made and people in the nearby Lubicon Cree community of Little Buffalo assured that the pipeline is safe.

But a spokesman for the premier's office, Cam Hantiuk, told CBC News that Stelmach had, in fact, said it was too early to evaluate the cleanup.

However, Stelmach did say he was "gobsmacked" when he heard that a company at another news conference, on Thursday, where an official had read a prepared statement and had taken no questions.

The statement read by Mike Hallahan, vice-president of Plains Midstream, tried to reassure the public that the spill doesn't pose a health threat to people who live in the region.

"Although there is an odour at the release site, the monitors at the site have detected no hydrocarbon levels above Alberta ambient air quality guidelines, and no negative health effects have been reported by workers on site to date," he said.

"These monitors have been in place since Monday and have detected no hydrocarbon levels whatsoever. We will continue monitoring air quality at the release site and in surrounding areas."

A school in Little Buffalo has been closed for a week. People in the area have reported getting headaches, feeling nauseous and smelling a strong petroleum odour.

Hantiuk added that Stelmach said the media may want to consider not attending future news conferences, if this is the way Plains treats the public.

Green Party wants investigation

Plains also took heat from the federal Green Party leader.

Elizabeth May Thursday called for an immediate investigation and serious consequences for the company if it is found to have been negligent.

"There has been a violation of the federal Fisheries Act, not to mention the negligence of failing to notify the public for five days," May said.

She also said the spill raises concerns about the safety of energy pipelines that criss-cross Canada and raises questions about industry plans to build more through ecologically sensitive parts of the country.

"We need to ensure a full investigation and serious sanctions," she added.

Plains Midstream Canada is a subsidiary of Houston-based Plains All American Pipeline, with pipelines and crude oil storage facilities throughout Alberta.

The leak was in the 44-year-old Rainbow pipeline which runs from Zama, Alta., to Edmonton.

With files from The Canadian Press