Problem with texture loading from resources

I’m having following code:

Texture tex = (Texture)Resources.Load ("1.bmp"); 
Debug.Log(tex == null); //prints true

File 1.bmp is in Resources folder, there’s a lot of free memory to load, but tex can’t be loaded, it is always null. How that could happen?

http://unity3d.com/support/documentation/ScriptReference/Resources.Load.html says “extensions must be omitted”.