About 20 houses and factories in Aspendale and Mordialloc were hit by what was reported as a mini tornado early this morning.

A State Emergency Services (SES) spokesman said buildings in the area received substanial damage when the tornado struck just after 2am.

Four SES units and 30 volunteers remain on the scene assisting residents to clear the area of debri and make structural repairs.

"We'll be going for most of the morning helping residents make temporary repairs to their homes," the spokesman said.

"Helping people repair damage to their roofs, make good their roofs to prevent any further damage. I assume as people get out of bed this morning we'll field more calls, as they find damage they weren't aware of overnight."

The Metropolitan Fire Brigade (MFB) also attended calls.

An MFB spokesman said the brigade attended the MordiallocChelsea Secondary School, which was missing part of its roof and a brick wall, and several homes in Aspendale where roofs were missing and power lines were brought down.

"We cleared some of the debri away and made sure there was no risk of fire," a MFB spokesman said.