Four energy companies are cleaning up crude oil that spilled into an unnamed creek in Strathcona County on Friday.

The creek, near 17th Street and Baseline Road, flows directly into the North Saskatchewan River.

Crews managed to contain the spill before it reached the river, Alberta Energy Regulator (AER) spokesperson Monica Hermary said Sunday. The size of the spill is still unclear.

"We will work with the companies to assess the cause of the incident," Hermary said. "Right now our focus is on ensuring that all safety and environmental requirements are met in response to the incident."

A team of Imperial Oil workers discovered the leak during routine maintenance.

Oil spilled along a pipeline right-of-way near the boundary between Strathcona County and Sherwood Park, a strip of industrial land where a number of companies have built pipelines.

Four companies could be responsible for the spill, Hermary said. She identified Imperial Oil, Gibson Energy, Inter Pipeline and Pembina Pipeline.

All four companies have shut in and de-pressurized their pipelines in the affected area and are helping with the cleanup.

Belinda de Wolde, a spokesperson for Imperial Oil, said the crude oil did not match her company's products when tested. Imperial Oil is leading the response to the incident.

"The current process, in addition to obviously recovering the oil, is determining where the source of the crude is," she added. "In other words, who the responsible party is. Then we would transition the recovery efforts to that company."

Crews discovered and contained the crude oil early, which de Wolde said has simplified the cleanup process.

"It's not a complicated site so it is moving quite quickly," she said.

Workers are using absorbent pads to soak up the spill. But on Sunday, de Wolde said it was still too early to estimate when crews would finish soaking up the spill.

"This is an operation that happens around the clock," she said. "No idea of how much longer it will take. We will carry on until the responsible party is identified."

The AER is overseeing the response to the incident. It is working with the companies, Alberta Environment and Parks and Environment Canada to ensure all safety and environmental requirements are met.