Crews are responding to a wildfire alongside the Sea to Sky Highway that was first reported early Sunday morning.

The BC Wildfire Service first heard of the fire at 3 a.m., according to spokeswoman Donna MacPherson. She told CTV News Vancouver the service had crews on scene by 4 a.m., and have been battling the blaze ever since.

As of the early afternoon, the fire remained out of control, and crews were having a hard time estimating its size because of the shape of the terrain, MacPherson said.

"The fire is burning on a very cliffy area," she said. "It's moving along the surface of the ground underneath the trees. So, as the crews are looking down through the trees, they're trying to ascertain about the smoke that they're looking at, whether that's indicating a drift or whether it's indicating the edge of the fire.

"Their best guess at this time is that it's somewhere around 3 hectares in size," MacPherson said.

Some 27 people from the wildfire service are battling the blaze, MacPherson said. The service had five helicopters and six fixed-wing aircraft, as well as an air attack officer coordinating the effort, she said.

Metro Vancouver Regional District Emergency Services tweeted that a total of 50 firefighters from several districts were involved in the effort: 

The wildfire service does not believe any structures are currently at risk from the blaze.

"There are some homes that are down slope and across the highway from the fire," MacPherson said. "But the fire is travelling uphill and a little bit to the side away from those structures, with the bit of wind that's on it now."

Northbound lanes of the Sea to Sky Highway are closed, with one lane of traffic remaining open in each direction. Traffic on the highway was moving slowly.

From the water in Howe Sound, flames could be seen at the base of trees growing out of the cliff.

Susan Rauter, general manager of Sunset Marina in West Vancouver, told CTV News that the power had been cut off to businesses and homes in the area. She said she has been receiving calls from customers asking if their boats are safe and whether they'll be able to get to them.

"It's a little scary right now, because it's fairly close to the marina," Rauter said. "They seem to be working at it really hard, so I don't know. Hopefully it doesn't come over the other side of the highway, down this way.

Videos posted on social media show significant smoke coming from trees right alongside the highway. 

The cause of the fire is still under investigation, but MacPherson said the wildfire service believes power lines may have been involved.

She said the area where the fire is burning is has a high fire danger rating due to drought conditions.

"Our drought codes are close to what they are at the end of July and the beginning of August," MacPherson said. "So it is very, very dry out there."

Sunday's weather forecast calls for possible showers in the evening, which would be welcome news for those battling the blaze.

MacPherson said the forecast is encouraging, with cooler temperatures and more showers projected through Thursday. The underlying drought conditions are unlikely to change, however.

"The slow, relentless task of getting this fire out is done by the crews on the ground," she said. "It would take a pretty heavy, steady rain to turn this drought around, and we're not seeing that level of rain in the forecast." 

This is a developing story. More details will be added as they become available.