  It is well-known that the central extensions of the loop group of a compact,
simple and 1-connected Lie group are parametrised by their level $k \in Z$.
This article concerns the question how much can be said for arbitrary $k \in R$
and we show that for each $k$ there exists a Lie groupoid which has the level
$k$ central extension as its quotient if $k \in Z$. By considering categorified
principal bundles we show, moreover, that the corresponding Lie groupoid has
the expected bundle structure.
