  We report millimeter interferometric observations of polarized continuum and
line emission from the massive star forming region G34.4. Polarized thermal
dust emission at 3 mm wavelength and CO $J=1 \to 0$ line emission were observed
using the Berkeley-Illinois-Maryland Association (BIMA) array. Our results show
a remarkably uniform polarization pattern in both dust and in CO J=$1 \to 0$
emission. In addition, the line emission presents a consistent uniform
polarization pattern over most of the velocity channel maps. These uniform
polarization patterns are aligned with the north-south main axis of the
filament between the main millimeter source (MM) and the ultra-compact H
{\scriptsize II} region, which are the central sources in G34.4, suggesting a
magnetic field orthogonal to this axis. This morphology is consistent with a
magnetically supported disk seen roughly edge-on.
