It was producing 165,000 barrels a day at the time. Officials with the Canada-Newfoundland Offshore Petroleum Board are investigating the incident on the floating production facility, located 350 km (217 miles) southeast of the Newfoundland coast.

"Production is still suspended and we're still awaiting conclusion of the investigation. We're co-operating with that and we're also doing some internal review," Petro-Canada spokesman John Downton said. "But it's not concluded yet, so I don't have a timeline."

Some authorities have called it the worst oil spill in the region. But it is tiny in comparison with the notorious Exxon Valdez spill that spilled 260,000 barrels of crude when the tanker ran aground in Alaska's Prince William Sound in 1989.

Petro-Canada said the main body of the slick covered a rectangular area of 6.1 kilometres (4 miles) by 5.5 kilometres (3.5 miles), and the only wildlife casualties reported so far were three oil-coated seabirds that were being treated.

Choppy seas were helping to disperse the oil, the company said, and clean-up equipment has been deployed at the scene.

The Atlantic coast spill has fueled debate over proposals to lift a moratorium on drilling on Canada's Pacific coast.

Provincial officials from British Columbia were in Ottawa this week urging the federal government to lift the ban, but green groups said the Terra Nova incident proved that current environmental rules for drilling were inadequate.