A longer than expected maintenance at a Shell refinery has resulted in another gasoline shortage at retail stations in Alberta.

The company's own stations, as well as others supplied by Shell, began running out of gas and diesel over the long weekend.

Scheduled maintenance work that began in early September at Shell's Scotford refinery in Fort Saskatchewan, near Edmonton, has gone on longer than expected, resulting in a shortfall in supply, said spokeswoman Jackie Panera.

"Although Shell secured sufficient fuel to cover this period, longer-than-planned maintenance activity, coupled with tight industry supply, has resulted in a temporary shortage of gas and diesel," she said.

"We do have plans in place to allocate amounts to customers so that we are trying to get the product out to customers as quickly and safely as possible."

Panera did not know when the maintenance would be done, but said the gas and diesel shortage could last for the rest of October.

She said Shell is looking at importing gas and diesel from other parts of Canada and the United States.

Shell won't say how many stations in Alberta are affected.

A major storm in August damaged equipment or knocked out power to Petro-Canada's refinery in Edmonton and Imperial Oil's facility in Strathcona County, leading to gas shortages at retail stations.