No one was supposed to be there

[Bobbert]

In a conversation, I was going to say, "No one was supposed to be there." I didn't actually say it because I was unsure of how to form the sentence. Now that I have time to think about it, I'm still unsure which is the best way and/or the correct way.

The possibilities that come to my mind are:

Se suponía que nadie había allí
No se suponía que nadie hubiera allí

Se suponía que nadie estaría allí
No se suponía que nadie estuviera allí

Se suponía que nadie debía estar allí

Any and all input and explanations are appreciated. The first words that come to my mind are using the verb "suponerse," so I would like to get input using that verb, if possible. However, using other constructions are also appreciated.