Overflights have continued and an remotely operated vehicle inspection is underway as the response continues to the shut-in of Husky Energy's White Rose field off the east coast of Canada following an oil spill amid poor weather conditions.

Husky said in a statement late on Monday that it believes that a subsea flowline is the source of the spill.

"Since the original spill, no additional oil has been detected at surface," the company said.

An update from the Regulator Canada-Newfoundland & Labrador Offshore Petroleum Board (CNLOPB) said that a flight this morning showed "no visible sheen" in areas covered.

"On-water monitoring continues. Another flight planned for this afternoon," the CNLOPB said in a midday statement.

It also added that the "Skandi Vinland supply vessel has deployed ROV to do subsea inspection," saying that a CNLOPB environmental officer was onboard to observe the ROV video.

Five oiled seabirds have been observed, Husky said, one up from the four reported by the regulator earlier on Monday, one of which may be retrieved for cleaning. A total of six vessels are deployed looking for wildlife impacts, with most seeing independent observers on board.

The CNLOPB previously said that "production and drilling operations are shut-in and will remain so for the foreseeable future" after the spill was noticed at the end of last week.

CNLOPB said that Husky has confirmed to it that all wells on the field have been shut in and are secure.

The spill came as severe weather hit the area, with CNLOPB describing conditions as "one of the worst this region has seen offshore since the Ocean Ranger disaster in 1982". That was in reference to the tragedy that saw the semi-submersible Ocean Ranger sink off Newfoundland, leaving 84 dead.

CNLOPB said on Friday that there was a loss of pressure from a subsea flowline to the SeaRose floating production, storage and offloading unit to the South White Rose drill centre, as Husky was preparing to restart production.

An initial estimate of the size of the spill was 250 cubic metres. No injuries were reported.

"The C-NLOPB is particularly grateful to the Canadian Coast Guard and the National Environmental Emergencies Centre for their ongoing assistance and advice in the board’s oversight of Husky Energy’s response to the spill.

"There is no reason to believe based on the flight results that this is an ongoing spill, and it is believed to be a 'batch spill'.

"Husky will deploy a Remote Operated Vehicle (ROV) to inspect subsea assets as soon as sea states have subsided to enable safe launching of the ROV.

"An updated estimate of the volume of the spill and other information should be available following the ROV deployment and subsea inspection."

CNLOPB said it will now formally investigate the incident and will "take whatever enforcement action is deemed appropriate in this incident".

Late last week, US supermajor ExxonMobil shut in production at its operated Hebron facility off Newfoundland due to rough weather conditions.

"For those following the weather offshore, we want to advise that all Hebron personnel are safe," the US supermajor said on Twitter on Friday.

"Earlier this morning Hebron shut in production due to adverse weather conditions. Safety is core to our operations and we continue to monitor the weather."

Hebron is about 200 miles (350 kilometers) off Newfoundland and Labrador and sits in some 300 feet of water (92 metres).

CNLOPB said on Frinay that ExxonMobil informed it on Thursday that "two out of three air handling units, located in the living quarters on the Hebron platform, were unavailable due to smoke in one of the living quarters’ electrical rooms".

"The smoke was due to a breaker fault from standby switchgear. All personnel mustered and there were no injuries.

"The fire team was dispatched and once it was confirmed the area was safe, personnel were released from muster.

"All production was shut down prior to the incident due to weather conditions."

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Oil spill shuts in Husky's White Rose