Mobil shut down a high-pressure pipeline at its Altona refinery in Australia early on Friday morning after a gas leak.

Fire crews were called out but the incident was quickly contained.

The company said that its employees responded promptly to safely contain the onsite release and shut down the effected unit. An emergency call was made to Melbourne's Metropolitan Fire Brigade (MFB), whose officers assisted Mobil in responding to the leak.

"Maintenance crews are repairing the problem at the moment, but the leak has been contained," an MFB spokesman told AAP on Friday morning.

Hoselines were used to protect the leak from ignition sources while the refinery shut down the pipeline.

The Maribyrnong & Hobsons Bay Star Weekly quoted MFB spokesman David Rankine, who said that Mobil's in-house safety equipment at the refinery worked well in shutting down the pipeline and capturing the gases to process through a filtration system.

"It was a protracted incident with a lot of specialist appliances on scene due to the nature of the emergency. However, most were just on stand-by or monitoring for hazardous gases," Rankine added.

Mobil confirmed on Friday afternoon that the company had completed the necessary repairs and was in the process of safely returning the refinery to normal operations.

The company apologized for "any inconvenience or concern that this incident may have caused our neighbors" and said it would conduct a thorough investigation into the cause of the release.