The Canadian Coast Guard is continuing to defend its response to the oil spill in Vancouver's English Bay last Wednesday, despite criticism from city and provincial officials.

Commissioner Jody Thomas said she was "enormously pleased" with the progress of the cleanup, and called the co-ordinated effort "unprecedented" while giving an update on the situation Monday morning.

The coast guard has been criticized for what was perceived as a slow response to the bunker fuel spill discovered last Wednesday around 5:10 p.m. PT. Many are also questioning why it took roughly 12 hours for the City of Vancouver to be notified.

But Thomas rejected that assessment, saying it took time to identify the source of the oil slick and the coast guard responded "very quickly."

"Within 25 minutes of notification, we were on the water. And with [Western Canada Marine Response Corporation], we worked through the night to skim the water and boom the ship."

"That's not a slow response."

Leak in ship identified, contained

Investigators have confirmed the vessel Marathassa was the source of the fuel spill, said Transport Canada Monday.

The agency's marine safety inspectors are still investigating the cause of the leak and owners of the vessel are co-operating fully, said Yvette Myers of Transport Canada.

Oil leaked from the fuel tank to the duct keel of the vessel, said Myers.

"On its own, it would have been a mess in the hull of the ship" and gone no further, she said. But, there was an unidentified "unrelated problem" that caused the oil to spill from the ship.

Investigators are still calculating how much oil was released, but estimate it at 2,700 litres.

The oil is viscous and buoyant, so boom containment on the surface of the water has been effective, said Randy Farrell, a coast guard pollution response officer. Shoreline cleanup continues, he said.

Premier's suggestion in 'the anger of the moment' dismissed

Earlier Monday in an interview on CBC Radio, Thomas also took exception to B.C. Premier Christy Clark's suggestion that the province would be able to do a better job of responding to spills like the one last week.

Clark said she was "very, very disappointed" it took six hours for booms to be placed around the vessel, and said it may be time for the federal government to hand over responsibility.

"Quite frankly, I just don't agree," Thomas told The Early Edition's Rick Cluff.

"Coast guard is mandated to respond. This is not a forest fire, it's a complex, multi-jurisdictional operation. I understand the anger of the moment, but I'm focused on what coast guard is doing and how effective coast guard has been in removing pollutant from the water."

To hear the full story, listen to the audio labelled: Coast guard CEO defends English Bay oil spill response