Crews worked Tuesday to start restoring water and electricity in this Canadian oil hub turned into a ghost town by a towering ring of fire that reduced its suburbs to ashes.

Government authorities, meanwhile, met with oil company executives in the oil sands region of unseasonably dry Alberta province to discuss how to get evacuated workers back on the job and production up and running again.

Oil is the lifeblood of the region's economy, and the fires raging around Fort McMurray for the past 10 days or so have led to a 40 percent drop in output.

Oil facilities have escaped major damage so far. But fires are still burning and officials said the main task is to keep them contained around those plants so workers can be flown back in.

Fire fighters using heavy machinery have cleared away swaths of forest around the oil facilities to keep the fire from spreading into them.

Another piece of bad news arrived Tuesday as health authorities reported an outbreak of gastronenteritis in shelters for people evacuated from Fort McMurray, with 105 cases tallied so far, most of them in one facility.

A ride through Fort McMurray showed the center of the now-empty city of 100,000 came out of the disaster largely intact. But the suburbs, where some people got just a half hour's notice to evacuate a week ago, were singed.

- Ruined suburbs -

The outlying areas are now a ruined, scorched landscape dotted with the odd survivor, like an elementary school here or a bus stop shelter there, coated in soot but still standing.

Plots of land where houses once stood are now separated by melted, twisted skeletons of metal fences.

Neat, nicely kept neighborhoods -- with single-family homes, yards with swing sets and houses for dogs -- are pretty much gone.

Outside one lot, a totally charred bike lies in the driveway of what had been a house. All that's left is a disfigured stove, covered in rubble and leaning against a blackened wall.

Fires are stilling burning to the east of the city. And the tally of how much land was charred now stands at 2,230 square kilometers (860 square miles), with 2,400 homes and other buildings destroyed.

As one approaches the city from the south on Highway 63, the lush green grass of springtime quickly gives way to scorched trees whose foliage went up in flames.

- 'Ocean of fire' -

Still, it could have been much, much, worse, said Alberta Premier Rachel Notley.

"The city was surrounded by an ocean of fire only a few days ago. But Fort McMurray and the surrounding communities have been saved and they will be rebuilt," she said Monday night.

"I've never seen anything like this," said city fire chief Darby Allen. "If that fire had gotten into the downtown, we would have lost the downtown area."

Inside the city, electrical utility crews got to work replacing wooden poles burned away by the fire, so they get power lines back up.

It will be at least two weeks before people can start returning to their homes, if they still have one, said Allen.

Of the 105 people who have come down with the stomach flu, 75 are staying at the largest fire-evacuee reception center, in Edmonton, the provincial capital, said Chris Sikora of Alberta Health Services.

More than 16,000 evacuees have passed through that center, officials said.