An anti-immigration billboard sign on Sahara nearParadise is now blank.  For weeks it was the target of controversy because it called for an end to immigration. It was funded by a white supremacist group called the National Alliance. We contacted Clear Channel Communications, which owns the billboard. But we have not heard back from it on why the sign is gone. The billboard is blamed for vandalism at nearby businesses. Those store owners said they were unfairly linked to the message above their businesses.