The explosion and fire at the Consumers' Co-operative Refineries Ltd. heavy oil upgrader in Regina on Thursday injured 13 people. Jordan Jackle/CBC

Two people remain in hospital following an explosion and fire at an oil refinery in north Regina on Thursday.

The blast and subsequent fire at Consumers' Co-operative Refineries Ltd. heavy oil upgrader injured a total of 13 people and caused 1,400 to be evacuated from the facility. Hours after the incident one person was reported to be in critical condition, another in serious-but-stable condition.

At a news conference Friday, however, representatives from the refinery and the Regina Qu'Appelle Health Region would not disclose any information about the types of injuries or the identities of those injured.

"I can't give you detail as far as the severity of any patients at this time," said Glen Perchie, executive director of emergency, EMS, and ambulatory care for the health region. "I cannot comment on that."

All of the injured people were contractors working on a $1.9 billion revamp of the refinery that is supposed to increase its crude processing ability from 100,000 barrels per day to 130,000 barrels.

The explosion happened at 2:05 p.m. CST Thursday in the diesel processing area of the plant where renovations were underway.

Official investigation to begin Sunday

The refinery said Thursday that it believed a leak in a pipeline pushed pressurized hydrogen gas and diesel into the air, where it found an ignition source.

The Regina fire department, the Office of the Fire Commissioner, and Occupational Health and Safety are expected to begin their official investigation into the cause on Sunday. Vic Huard, vice president of corporate affairs with Federated Co-operatives Ltd., said he does not know how long it will take.

"We're co-operating fully with that, but this investigation is independent of [Consumers' Co-operative Refineries Ltd.] and [Federated Co-operatives Ltd.] and cause will be determined by those agencies, not by us," said Huard. "So I'm not prepared to comment on cause because we simply don't know."

The area of the refinery where the explosion happened will remain locked down for an indeterminate amount of time. Gasoline production has been curtailed by 50 per cent and diesel output by 20 per cent at the complex, Huard said. He estimated gasoline production would be back to normal within 72 hours, whereas diesel production will take longer to ramp back up.

In the meantime, all 450 of the refinery employees were back at work on their regular rotating shifts. However, 1,000 contractors working around the blast area are off the job until the investigation is done and the area can be declared safe. The company has brought counsellors in to help any employees who were affected by the explosion.

"We're very concerned about our people, and we're doing what we can to make sure they're taken care of," said Huard. "I can't say enough about the job they're doing and their focus and professionalism."