Same as Fig. 2 for the three MDCs located in the filament of DR21 (see text). Note that in contrast to the isolated MDCs (Fig. 2), the cores show here diverse structures. CygX-N40 appears devoid of compact emission at both 3.5 and 1.3 mm. CygX-N48 has a complex and extended structure at 3.5 mm with two main cores in the central regions. The 1.3 mm emission resolves a few, probable compact, fragments in the two main cores. CygX-N53 has a bright central core at 3.5 mm that divides into 4 smaller fragments at 1.3 mm in a way similar to the isolated MDCs. The bright peak at 3.5 mm in the south-east corresponds to the weak 1.3 mm source outside in the primary beam (dashed circle) in the right panel. It is located at the edge of the nearby cluster associated with MSX6G81.7133+0.5589.