A massive wildfire in a popular Delta, B.C. conservation area has stopped growing, and is about 50 per cent contained.

On Monday afternoon, Delta Fire Chief Dan Copeland said crews have made "significant progress" in the fight against the Burns Bog fire, and now have a better idea of its size. GPS coordinates show the blaze reached 78 hectares, more than the initial estimate of between 55 and 70.

"That's not that it's grown, it's actually the exact size of the fire. We had no fire extension overnight and the crews are working hard to extinguish," Copeland said at a news conference.

The fire chief said crews had spent the morning focusing on the north flank of the fire, trying to prevent it from spreading to an industrial area.

As of 3:30 p.m., half of the fire was contained, but Copeland said they expect to have "significantly more than that" under control by the end of the working day. When efforts began Monday morning, only 10 per cent of the fire had been contained, though crews had been at the scene all afternoon Sunday.

Provincial fire crews were called in to assist several hours after flames erupted. Forty provincial firefighters, aided by four helicopters and five air tankers, joined the effort, and in total around 100 firefighters battled the blaze.

One firefighter was taken to hospital to be treated for a medical condition that worsened because of environmental conditions at the fire scene. That person is now in stable condition at Royal Columbian Hospital.

Copeland said ground crews will be working until 8 p.m., and helicopters will finish an hour earlier.

At the height of the fire, the nearby Tilbury business centre was evacuated as flames and smoke threatened the area. The evacuation will be lifted at 8 p.m., Delta Police Chief Neil Dubord told reporters, and anyone on night shifts will be allowed back to work.

"However... It is a dynamic fire still and there may be further evacuations as we move forward, but we do not expect that at this particular time," Dubord said.

Highway 17, which was closed between Highway 99 and the Highway 91 connector, will remain closed likely until Friday, he said. Firefighters are using the road to move equipment and personnel safely, so the section will remain closed until their efforts are over.

Initial fears were that the fire would get under the peat of the bog, allowing it to travel a further distance.

The 3,000 hectare peat bog is one of North America's largest, and fire can burn under the dry peat, out of sight. In 2005, a fire in the bog spanning two kilometres burned for one week before crews could put it out.

"Apparently it hasn't done this in this location, one of the main reasons being that we got there very quickly," Mayor Lois Jackson said.

Smoke from the Burns Bog fire blanketed parts of Metro Vancouver Monday, but the smoky skies did not trigger an air quality advisory.

Jackson said the highest concentration of particulate in the air happened between 8 p.m. and midnight Sunday, but conditions improved overnight.

Once the fire is over, Jackson said the city will request a debrief with Metro Vancouver's Burns Bog Scientific Advisory Panel to kickstart recovery and preservation efforts.

Though the bog itself will return to about 90 per cent of its efficiency in a few years, the fire has destroyed dozens of hectares of habitat for 175 species of birds.

Wildlife experts said they're especially concerned because of the timing of the fire, in the middle of fledgling season for birds of prey.

Falcons, eagles and hawks are likely too young to leave the nest at this time of year.

"They're going to get burned to a crisp," Burns Bog Conservation Society president Eliza Olsen told CTV News.

And the birds that do survive will have more competition for food with the insect population depleted by fire.

The cause of the fire has not been determined.