A device for depolluting a heat engine exhaust gases includes an outer casing (23) delimiting an exhaust gas circulating passageway and a particle filter (20) mounted in the passageway. The casing (23) includes a transverse break (34) along its entire periphery, the break (34) dividing the casing (23) into first and second successive segments (38, 40). The first and second successive segments (38, 40) include two mutually engaged ends. One outer end of the first segment (38) overlaps one inner end of the second section (40) along part of the length of the flow passageway. The outer end of the first segment (38) includes along its periphery at least one weakened region (50) for varying the cross-section of the outer end of the first segment (38). The device is applicable to motor vehicles.