(Refiles to show in 7th paragraph that Imperial Oil provides operational support to Syncrude under a services agreement, not that Imperial is the operator)
By Nia Williams and Ethan Lou
CALGARY, Alberta, March 14 (Reuters) - One worker was injured in a fire at the Syncrude oil sand plant in northern Alberta on Tuesday, which emergency crews got under control roughly four hours after it started, a company spokesman said.
An explosion rocked the 350,000 barrel per day upgrading facility at around 2 p.m. local time, prompting an evacuation, employees on site at the time said. Syncrude is situated about 40 kilometers north of the oil sands hub of Fort McMurray.
"Syncrude Emergency Services and Operations personnel have isolated and controlled a fire that occurred in the Mildred Lake Upgrader this afternoon," the company said in a statement.
Syncrude spokesman Will Gibson said the company did not know the cause of the fire and would release details as soon as they were available.
"The employee was transported to the hospital and family has been notified," Gibson added on a phone call.
The injured worker is in a serious but stable condition, Alberta Health Services spokesman Kerry Williamson said on a phone call.
Syncrude, Canada's largest single source of synthetic crude, is majority-owned by Suncor Energy while Imperial Oil provides operational, technical and business management support under a services agreement signed in 2006.
Videos posted on social media showed flames leaping above a facility and a plume of black smoke billowing into the sky.
Local emergency services posted a health advisory after the incident, saying a fire was reducing air quality in the nearby community of Fort McKay and asking people to stay indoors.
Gibson said access to the site had been restricted.
Syncrude, like many oil sands plants, has its own on-site fire department. Last May those firefighters battled to save the facility from uncontrolled wildfires that raged through the Fort McMurray oiltown region.
Light synthetic crude prices for April delivery jumped in the last half hour of trading on Tuesday on the prospect of reduced supply, with prices surging 50 cents to settle at 90 cents per barrel over the West Texas Intermediate benchmark, according to Shorcan Energy brokers.
The Royal Canadian Mounted Police said officers received a call about the fire at 2:15 p.m. and were at the scene along with other emergency services. They asked people to avoid the area and temporarily closed the highway nearby.
The Alberta Energy Regulator said it has dispatched staff to the scene. (Editing by Richard Chang and Leslie Adler)