  We report results of 14N-NMR experiments on NH4CuCl3 at the magnetic field of
7 T, where the 1/4-magnetization plateau is observed at low temperatures. The
quadrupole splitting parameter $\nu_{z}$ splits below 70 K, indicating a
structural phase transition. At 4.2 K, eight N sites with distinct values of
both $\nu_{z}$ and the magnetic hyperfine shift $K_{z}$ are resolved in the NMR
spectrum for general field directions. We then conlude that the magnetic
structure in the 1/4-plateau does not break the symmetry of the crystal. Based
on the NMR and the recent neutron scattering results by Ruegg et al. [Phys.
Rev. Lett. 93 (2004) 037207], we propose that triplet dimers in the 1/4-plateau
is formed not between the nearest neighbor pairs but over different chains.
