Syncrude said the fire in the Mildred Lake Upgrader area was extinguished Thursday morning.

The fire, which has been under control since Tuesday afternoon, began with an explosion blamed on a naphtha leak at around 1:50 p.m.

“My deepest appreciation goes out to everyone who responded to this incident,” Syncrude CEO Mark Ward said in a press release. “This remains a difficult time for our organization, but I am proud of the tireless efforts of our employees to ensure the safety and stability of our operations.”

The employee injured during the fire is in stable condition in an Edmonton hospital, Syncrude said.

The area of the explosion and fire is being isolated to allow Alberta Occupational Health and Safety to investigate the incident.