Overlays of the velocity-integrated maps of CO (3–2) (left column), CO (4–3) (middle column), and CO (7–6) (right column) as white contours on the CO (6–5) emission (colour background) observed towards W44E with the APEX telescope. The maps are in their original resolution (9 for CO (6–5), 13 for CO (4–3), and 18 for CO (3–2)), except for CO (7–6), which was smoothed to the resolution of CO (4–3) in order to improve the signal-to-noise. The intensity was integrated between 20–40 km s^-1 (blue wing, top row), 40–50 km s^-1 (ambient emission, middle row), and 50–70 km s^-1 (red wing, bottom row). The wedge unit is K km s^-1 in antenna temperature. The contours are in steps of 10%. The half-maximum contours of the colour and contour maps are indicated in red and black, respectively. The blue and black circles indicate the positions of our shock modelling analysis. The APEX beam sizes of the observations displayed are given in the upper left corner of each map. The black and blue hexagons mark the positions of the OH masers observed by Claussen et al. (1997) and Hoffman et al. (2005). At the assumed distance of 3 kpc the 9 beam of CO (6–5) corresponds to a spatial resolution of 0.13 pc.