How to use different Entity Framework DbContext in the Area of ASP.NET MVC application?

Currently I am building a web application with MVC 4 and Entity Framework code first scenario.

In the main structure of my application, I have a Dbcontext(BlogDB) to manage some Blog classes. It works fine as it created all the tables I need in the database. Then I created a Area to host an online store. My idea is to create a separated DbContext class(OnlineStoreDB) to handle the classes used for Online Store only.

My problem is once the OnlineStoreDB is fired, entity framework not only created tables for OnlineStore BUT ALSO removed old tables.

My questions are:

1. If you know a way to keep the old tables?
2. How exactly to manage the multi EF context classes in one application?

Code:

public class BlogDB : DbContext
{
    public BlogDB ()
        : base("DBConnection")
    {
        Database.SetInitializer(new BlogInitializer());
    }

    public DbSet<Blog> Blogs { get; set; }
    public DbSet<Author> Authors { get; set; }
    public DbSet<Comment> Comments { get; set; }
}

public class OnlineStoreDB : DbContext
{
    public OnlineStoreDB() :
        base("DbConnection")
    {
        Database.SetInitializer(new OnlineStoreInitializer());
    }

    public DbSet<Order> Orders { get; set; }
    public DbSet<Product> Products { get; set; }
    public DbSet<User> Users { get; set; }
}