Police have disabled a pipe bomb found at a school in Warrnambool in a controlled detonation.

Victoria Police's bomb squad detonated the device at 7.30pm, about five hours after it was found near a bus shelter at the front of Brauer College in the state's south-west.

The bomb found outside Brauer College. Credit:Warrnambool Standard/Supplied

A police spokeswoman said arson chemists will now examine the device, which has been "rendered safe", while local detectives continue investigating how and why it was left there.

The school was locked-down after the discovery and a 100 metre exclusion zone was put into place, the Warrnambool Standard reported.