FOSS gamedev and creative worlds

I have installed the mobs mod and then after running minetest, I decided I wanted to get rid of the rats. I removed all references to them in init.lua, deleted the bitmap and the x file. I still get a message "ERROR.........."mobs rat" not defined" How can I get rid of rats?

Use "/clearobjects", see http://wiki.minetest.com/wiki/Server_commands