Is there a Risk of Tail Tipping during Push-back of a passenger aircraft? I remember that there were countless incidents occurred in which the aircraft sits on the tail as the aircraft was heavily loaded at the back of the cargo and/or cabin compartments or the cargo compartments were offloaded incorrect order. I know that these incidents are more commonly happen in cargo aircrafts. 

Is there a risk that the aircraft will sit on the tail during the pushback process as a result of the tri-cycle design of the aircraft? 

Is there any tail tipping incident reported during pushback/towing operation? 

Which types of aircraft (narrow/wide body) can this risk be higher?
During pushback the (usually quite substantial) weight of the tug pulls the nose down, and additionally when it's pushing backward the line of force is below the CG and acting rearward, so that would also tend to counteract any tipover tendency.

As Jan mentions in comments, the tipover situations tend to happen during loading when the CG is moving around. I suppose if the tug were first attached and then the aircraft were grossly misloaded, it's conceivable that it could tip over backward as the tug detaches and removes it's weight, but I've never heard of that happening.