  In this note we construct a series of singular vectors in universal affine
vertex operator algebras associated to $D_{\ell}^{(1)}$ of levels $n-\ell+1$,
for $n \in \Z_{>0}$. For $n=1$, we study the representation theory of the
quotient vertex operator algebra modulo the ideal generated by that singular
vector. In the case $\ell =4$, we show that the adjoint module is the unique
irreducible ordinary module for simple vertex operator algebra
$L_{D_{4}}(-2,0)$. We also show that the maximal ideal in associated universal
affine vertex algebra is generated by three singular vectors.

Quantum Algebra