First Nations on B.C.'s Central Coast are worried about environmental damage after a tug boat that left Alaska with nearly 200,000 litres of diesel fuel ran aground early Thursday morning near Bella Bella.

The Nathan E. Stewart and the empty fuel barge DBL 55 crashed on Edge Reef, in Seaforth Channel near Athlone Island, just after 1 a.m. PT, Thursday. While the fuel barge was empty, the tug was leaking diesel.

The tug and barge are owned by the U.S. company Kirby Offshore Marine. It said the Western Canada Marine Response Corporation has deployed vessels and crew from a base in Prince Rupert several hundred kilometres away.

"A mobile skimming vessel, boom skiff, work boat, and tug, along with a total of 2,500 feet of boom, have been deployed to the scene," Jim Guidry, Kirby's incident commander, said in a statement.

"Owners and managers of the Nathan E. Stewart regret that this incident has occurred and are working to respond and mitigate the impact."

Late in the day, Guirdy issued another statement, saying the tug had nearly 200,000 litres of diesel fuel when it began its voyage and that resources to meet "a worst possible discharge" had been activated.

"A priority for the response will be developing a plan to remove all diesel aboard the tug and to safely salvage the vessel," he said.

An aerial photo of the sinking tug boat. (Elizabeth Harris)

Members of the Heiltsuk Nation responded to the scene, along with the Canadian Coast Guard, and are monitoring the environmental effects of the spill.

They reported that three fuel tanks on the tug had been compromised and that the vessel had sunk.

"Things don't sound promising from the chatter we are hearing on the radio," said Heiltsuk tribal councillor Jess Housty.

The Coast Guard confirmed the tug sank but said it is still connected to the barge, which is stable.

"The tug is submerged and leaking some diesel, which is expected to dissipate and break-up," said Coast Guard spokeswoman Michelle Imbeau in an email.

The sheen of diesel can be seen on the water near where the tug boat sank after running aground. (Ingmar Lee)

The spill threatens dozens of species that are harvested in the area, including manila clam beds that provide income of up to $150,000 per year for the community, according to the Heiltsuk.

"It's a significant part of our local winter economy. That clam fishery was due to open in about three weeks," said Marilyn Slett, chief councillor for the Heiltsuk Tribal Council.

Slett said the nearby Gitga'at Nation is still unable to harvest seaweed and clams because of pollution from the sinking of the Queen of the North ferry a decade ago.

Vessel had pilotage exemption

Seven people were onboard the tug at the time of the grounding. No injuries were reported, said Imbeau.

Weather conditions provided for visibility of eight miles when the tug and barge ran aground, and the wind was blowing at nine knots, she said.

The Heiltsuk Nation is worried diesel that escaped from the damaged tug boat will contaminate the environmentally-sensitive harvesting area. (Elizabeth Brown)

The incident shows the need for improved spill response for the area, the Heiltsuk Nation said, adding it could take up to 24 hours for spill response ships to arrive from Prince Rupert.

U.S. vessels that are under 10,000 gross tonnage, such as the Nathan E. Stewart, are often allowed to operate without a local pilot on the West Coast of Canada, if the crew meets a minimum standard of experience and licensing, said Kevin Obermeyer, CEO for the Pacific Pilotage Authority.

"We've removed the waiver pending [the] result of [the] investigation," he said.

With files from Ash Kelly, George Baker, Andrew Kurjata