Both of the Ballarat-bound and Melbourne-bound lanes of the Western Freeway near Myrniong and Pentland Hills have been closed, and major delays are expected after several separate crashes believed to have involved more than 20 vehicles. The westbound lanes of the freeway have been closed at Mortons Road at Pentland Hills while the eastbound lanes are blocked by emergency services near Pykes Creek. A Victoria Police spokesperson said multiple cars are involved in the incident, but there are no reports of serious injuries at this stage. "It's believed more than 20 vehicles are involved due to heavy fog in the area," the spokesperson said. "Please avoid the area." A Department of Transport and Planning spokesperson said the fog was making it difficult for drivers to see. "Rain and fog decrease visibility - in foggy conditions, use fog lights instead of setting your headlights on high beam. If you don't have fog lights you can use your hazard lights with your headlights on low beam," the spokesperson said. "Every road user, including heavy vehicles, need more space to brake on wet roads - drivers and riders should allow at least four seconds between them and the car in front and adjust their speed to the conditions." Police, firefighters and paramedics on scene. MORE TO COME.