Nov. 20 (Bloomberg) -- Royal Dutch Shell Plc, Europe's biggest oil company, said a fire reduced output by more than half from a plant that processes bitumen from Alberta's oil sands into synthetic crude oil.

The fire occurred at one of the Scotford Upgrader's two residue hydroconversion units at about 4 p.m. local time yesterday and was extinguished within an hour, Shell's Canadian unit said. No injuries were reported. The Alberta Energy & Utilities Board said on its Web site it was investigating the incident.

The ``majority'' of the plant's daily output of 155,000 barrels of bitumen was halted, plant spokesman Randy Provencal said in an interview today without elaborating.

The fire was caused by a leak of ``hydrogen, some light hydrocarbons and some hydrogen sulfide,'' which has now been contained, Shell Canada said in a statement late yesterday.

Shell Canada yesterday also reported a sour-gas release from a pipeline in the Waterton gas field southwest of Pincher Creek. The incident occurred at about 9:15 a.m. local time, and emergency shutdown valves ``successfully isolated the affected section of the pipeline and brought the situation under control,'' the company said in a statement on its Web site.

No injuries were reported. Shell evacuated five people from the area, spokeswoman Saskia Kapinga said from London. ``As a precaution, we've decided to voluntarily shut in production operations in the area until the cause of the accident is known,'' she said.

Kapinga declined to comment on the impact on actual output volumes and when pumping will resume in the Waterton field area.

Staff and ``air monitoring equipment'' from the Alberta Energy & Utilities Board are on site to conduct an investigation, the agency said. ``Pipeline failures in Alberta are rare,'' it said.

To contact the reporters on this story: Christian Schmollinger in Singapore at Christian.s@bloomberg.net; Sonja Franklin in Calgary at sfranklin6@bloomberg.net.

Last Updated: November 20, 2007 10:41 EST