What is the correct action to take first if a fire breaks out in the cargo compartment of a vehicle carrying flammable liquids?

1. Try to extinguish the fire immediately using the 2 kg cab extinguisher
2. Stop the vehicle safely, apply the handbrake, switch off the engine, evacuate the area, and contact the emergency services (999/112)
3. Drive as fast as possible to the nearest fire station to get help
4. Climb onto the roof of the cargo area to inspect the source of the fire