A truck lost its load of offal on the Princes Freeway on Thursday, causing heavy delays during the afternoon commuter peak.

Animal entrails spilled across the road in Laverton, south-west of Melbourne, about 3.50pm.

It's believed the butcher's truck braked heavily to avoid a collision, causing the truck to lose its load.

"It's made the road really greasy and wet," Victoria Police media officer Creina O'Grady said after the incident.