Canadian Coast Guard officials said Thursday the estimated size of an oil spill in English Bay had nearly doubled from 1,400 litres to 2,700 litres, or more than two tonnes.

Assistant Commissioner Roger Girouard also revealed at a news conference Thursday night that a sizeable slick 15 to 20 centimetres deep and covering about 80 metres had reached the North Shore.

Girourad. said that despite the size of the unexpected slick off West Vancouver's Sandy Cove and the larger-than-estimated size of the spill, officials still believe it is about 80 per cent contained.

Crews on spill response boats work around the bulk carrier cargo ship Marathassa after a bunker fuel spill on English Bay in Vancouver, B.C., on Thursday April 9, 2015. (Darryl Dyck/The Canadian Press)

"As the sun sets here and we bring in assets from the water, most of the Western Canada Marine vessels [tasked with oil recovery] are quite confident that the lion's share of the oily material that was in the bay has now been recovered." he said."

Despite claiming the spill was under control, Girouard admitted the fact the slick has reached West Vancouver took them by surprise.

"It is being reviewed and assessed with a response and cleanup at first light," he said. "In the grand scheme that's not a major eventuality, but certainly an area of concern for the residents of the North Shore, so we're responding with some vigor to make sure that's cleaned up."

Residents asked to not help cleanup

Girouard said the Coast Guard didn't see a major risk to area beaches from the spill, but planned to make beach cleanup a priority over the next several days and asked residents to stay away from the shoreline on both sides of the bay until the beaches are cleared.

Beaches on the Vancouver side also showed signs of contamination Thursday.

"Keep your pets off the beaches," Girouard said. "And just give us some time to get our arms around what segments do need to be cleaned up," he said.

A spill response boat secures a boom around the bulk carrier cargo ship Marathassa after a bunker fuel spill on Burrard Inlet in Vancouver, B.C., on Thursday April 9, 2015. (Darryl Dyck/The Canadian Press)

"I'd also ask people not to do freelance cleanup on their own for their own health and safety. We are concerned about getting rid of the waste material. You can't just put that kind of thing in your dumpster."

He said it's still not clear whether the bulk carrier, the Marathassa, which is currently encased in booms, is the actual source of the spill.

"There was an indication late this afternoon that more fresh oily material had shown up inside the boom and so we have a slight disconnect between what appears to be the fitness of the hull and this new material," he said.

"We cannot say absolutely the source of this oil is this vessel," he added. "As I said earlier, middle of the [oil] bull's-eye was this vessel, but we still have to go through the process of proving where the oil is from."

Girouard said an initial investigation by Transport Canada divers and investigators on the vessel was inconclusive, but the federal agency was taking samples. He said the forensic part of the investigation could take a little time.

A Coast Guard flyover in the late afternoon detected no major oil slicks said Girouard, but the plane would be back in the air Friday morning having another look.

Anyone who spots an oil slick in the water or ashore is asked to call a clean-up hotline at 604-873-7000.

MAP: Sandy Cove, West Vancouver