Preheat oven to 375°F (190°C). Line a muffin tin with paper liners.
In a large bowl, mix together flour, sugar, salt, and baking powder.
In another bowl, combine vegetable oil, egg, and milk. Add to the flour mixture and stir until just combined.
Gently fold in blueberries.
In a small bowl, beat cream cheese, sugar, and vanilla extract until smooth.
Fill muffin cups halfway with batter. Add a teaspoon of cream cheese mixture in the center of each. Top with remaining batter.
Bake for 20-25 minutes or until a toothpick inserted into the muffin comes out clean.
Cool in the pan for 5 minutes, then transfer to a wire rack to cool completely.