Chemical leak at Mobil's Altona refinery

Firefighters have contained a chemical leak at Mobil's oil refinery at Altona in Melbourne's southwest.

Firefighters have contained a chemical leak at Mobil's oil refinery in Altona. (AAP)

Specialist firefighters have contained a chemical leak at the Mobil oil refinery in Altona in southwestern Melbourne.

Hazmat crews handed back control of the site to Mobil just before 7am after the leak that was identified as a mixture of hydrogen and naptha.

The site operates 24 hours a day and can produce up 13 million litres of refined products each day.