Only about six litres of oil remained in B.C.'s English Bay late on Friday night when a Transport Canada plane flew over the site of the recent spill, and most of that would have evaporated overnight, according to a Canadian Coast Guard official.

Assistant commissioner Roger Girouard said on Saturday there is currently no indication of distress among marine mammals, but a number of teams are on the water monitoring the situation.

"The small number of birds impacted is an indicator of how successful we were getting the oil as fast as possible," Girouard said at a morning news conference.

An estimated 2,700 litres, or more than two tonnes, of oil was spilled on Wednesday.

Girouard said the focus now turns to what he described as the small amount of oil that managed to make it to shore

"On the shoreline, every indication we have is the soiling is in fact minor," he said. "There are a couple of spots where a one-metre globule got onto some rock, but in the main, even on the worst-impacted site in West Vancouver, thankfully the impact is relatively minor."

"That does not mean we won't address it."

Girouard said crews will work on shoreline cleanup over the next several days.

"Today, we have a full day of teams on the beach," he said. "That will continue throughout the weekend and into the week."

Residents asked not to assist

He reiterated the coast guard's earlier request that residents not assist with cleanup efforts.

The spilled bunker fuel is "not healthy stuff," he said. "You will see signs at the beach to stay clear of the water. Please don't get into a venture of doing your own cleanup and don't do any wildlife assistance on your own. Call us and let the experts do their work."

Roger Girouard, assistant commissioner of the Canadian Coast Guard, says oil removal is going well, but asked residents not to help because the spilled bunker fuel requires professional cleanup crews. (CBC)

Girouard said the source of the leak has been traced to a hull outlet on the Marathassa, a Cypriot-registered bulk carrier recently built in Japan.

He said the vessel meets all modern standards and was on its maiden voyage. It was anchored in the harbour waiting to take on a load of grain when it began leaking oil.

Girouard said the fact that the Marathassa is a modern ship, recently built, makes the spill all the more puzzling.

The company that owns the ship is based in Greece, but it sails under the flag of Cyprus — a well-known flag of convenience in the shipping industry. Ships traditionally register with countries where labour is less expensive or safety regulations are more lax.