The action comes as a series of public hearings on the pipeline by a joint panel of the National Energy Board and Environment Canada are set to begin Tuesday and continue into March. More than 4,000 people have registered to testify.
The 745-mile proposed pipeline can carry up to 525,000 barrels of oil a day from oil sands projects in Alberta to the British Columbia coast, opening the Alberta oil sands to Asian markets, including China.
Each of the five companies -- Cenovus Energy Inc., MEG Energy Corp., Nexen Inc., Suncor Energy Inc. and Total E&P Canada -- has signed up as a "funding participant" in the proposed pipeline, The Globe and Mail newspaper in Toronto reported.
Chinese state-owned oil company Sinopec had previously been identified as one of the funding participants.
"The more business partners that we have step up to the plate and add their voice to that momentum, the better we are for that," Gateway spokesman Paul Stanway told the newspaper. "We're seeing a groundswell of opinion in favor of Northern Gateway."
The results of a survey by polling firm Ipsos Reid on behalf of Enbridge released this week indicated that 48 percent of British Columbia residents asked expressed support the project while 32 percent said they were opposed to it. Yet only 42 percent said they were familiar with the proposed pipeline.
Still, 130 First Nations have vowed to block the Northern Gateway project and it faces fierce opposition from a slew of environmental groups including the Natural Resources Defense Council, Pacific Wild, Sierra Club BC and ForestEthics.
They are concerned about the chances of a major pipeline rupture or tanker spill.
In July 2010 an Enbridge pipeline ruptured in Michigan, in which the company said 840,000 gallons of oil spilled into the Kalamazoo River and Talmadge Creek. But the EPA reported that 1,139,569 gallons of oil had been recovered, including oily water, soil, sediment and debris.
Stanway, speaking to The Vancouver Sun, maintained that the company "[takes] lessons from that situation and [will] use that information to ensure nothing similar to it can happen again."
And the Canadian government is "committed to a thorough environmental assessment and consultation with aboriginal groups," about the project, Minister of Natural Resources Joe Oliver told the Sun, noting that it has the potential to generate hundreds of thousands of new jobs, trillions [of dollars] in economic benefits," as well as billions of dollars in taxes and royalties to support government services.