(see arrows in Figures \[fig7\]a and \[fig7\]b). Similar result is also derived using the distribution of the radial velocities of the ATLASGAL clumps (see Figure \[fig4\]b). In the velocity space, the cloud components around 35 and 53 km s$^{-1}$ appear to be connected by a low-intensity intermediate velocity emission around 45 km s$^{-1}$ (see red broken curves toward [*l*]{} = 13$\degr$.1–13$\degr$.2 and [*l*]{} = 12$\degr$.7–12$\degr$.8 in Figure \[fig7\]a). Based on the observed different velocity components, Figures \[fig8\]a, \[fig8\]c, and \[fig8\]e show the spatial distribution of $^{13}$CO gas associated with the clouds at \[29.6, 43.3\], \[44, 46.5\], and \[47.2, 60.2\] km s$^{-1}$, respectively. In Figures \[fig8\]b, \[fig8\]d, and \[fig8\]f, we present the distribution of C$^{18}$O gas associated with the clouds at \[29.6, 43.3\], \[44, 46.5\], and \[47.2, 60.2\] km s$^{-1}$, respectively. In each panel of Figure \[fig8\], the positions of W33 A, W33 B, and W33 Main are also highlighted by open circles, while the positions of three O4-7I stars [see IDs \#7, 8, and 23 in @messineo15] are shown by filled stars (in cyan). The sites W33 A and W33 Main are seen with the highest intensities in the $^{13}$CO and C$^{18}$O maps at \[29.6, 43.3\] km s$^{-1}$, while the 