Left: the W28 complex on large scales. Grayscale (in σ) and thick contours show TeV emission as seen by HESS (levels are 4−6σ). Red contours show the CO(1−0) emission (Dame et al. 2001) integrated over 15−25 km s^-1 and magenta contours trace the emission integrated over 5−15 km s^-1 (levels are 40−70 K km s^-1 by 5 K km s^-1). Crosses show the positions observed with the IRAM 30m telescope and discussed in this paper. The blue contours show the 20 cm free-free emission in the M20 region (Yusef-Zadeh et al. 2000). The blue circle gives the approximate radio boundary of the SNR W28 (Brogan et al. 2006). Right: the northern cloud in the W28 complex (zoom on the black box). The red contours show the CO(3−2) emission in K km s^-1, integrated over 15−25 km s^-1 (levels are 15−130 K km s^-1 by 5 K km s^-1) (Lefloch et al. 2008). Diamonds show the locations of OH masers in the region (Claussen et al. 1997).