  We used MIDI, the mid-infrared interferometric instrument of the VLTI, to
observe the massive protostellar candidate IRS 9A, located at a distance of
about 7 kpc at the periphery of the NGC 3603 star cluster. Our ongoing analysis
shows that MIDI almost fully resolves the object on all observed baselines, yet
below 9 $\mu$m we detect a steep rise of the visibility. This feature is
modelled as a combination of a compact hot component and a resolved warm
envelope which lowers the correlated flux at longer wavelengths. The extended
envelope can already be seen in both MIDI's acquisition images and in
complementary data from aperture masking observations at the Gemini South
telescope. Its shape is asymmetric, which could indicate a circumstellar disk
inclined against the line of sight. The compact component is possibly related
to the inner edge of this (accretion) disk. The uncorrelated mid-infrared
spectrum appears featureless and could be caused by optically thick emission
without a significant contribution from the disk atmosphere.
