**Table 1:** Basic and derived data for observed targets. Magnitudes and colours are taken from the 2MASS database, except for IRAS 17175-3544 by Tapia et al. (1996).
IRAS	H	J-H	H-K	$A_{\rm v}$	Sp.T.	Int./s
17175-3544^a	14.00	2.75	3.43	>13^d	O6-O7	7560
17441-2910^b	10.29	3.42	2.41	30	O5.5	480
18079-1756^c	11.09	2.67	1.67	74	B	960

^a Walsh et al. (1999).
^b Porter et al. (1998), Walsh et al. (1997).
^c Osterloh et al. (1997).
^d Using the given spectral type and using a distance of 2.2 kpc (see text) we derive $m_{\rm v}=6$ ,
yet there is no optical counterpart on DSS plates.

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