what causes white smoke from exhaust

White smoke from a car's exhaust is often a sign that coolant is being burned in the engine. This can be caused by a blown head gasket, a cracked engine block, or a cracked cylinder head. Other possible causes of white smoke from the exhaust include water in the exhaust, over-fueling, or a bad spark plug. However, the most common cause is a problem with the engine's cooling system, such as a blown head gasket. It's important to have the issue diagnosed and repaired by a qualified mechanic to prevent further damage to the engine