What is the cleanest way to disable CSS transition effects temporarily?

I have a DOM element with some/all of the following effects applied:

#elem {
  -webkit-transition: height 0.4s ease;
  -moz-transition: height 0.4s ease;
  -o-transition: height 0.4s ease;
  transition: height 0.4s ease;
}

I am writing a jQuery plugin that is resizing this element, I need to disable these effects temporarily so I can resize it smoothly.

What is the most elegant way of disabling these effects temporarily (and then re-enabling them), given they may be applied from parents or may not be applied at all.