Masers in the blue group (blue triangles and blue segments) superimposed on the integrated I image of the dust continuum emission observed by Beuther et al. (2010) at 880 μm with SMA (red contours; the contours are drawn in 10σ steps). The magenta line segments show the magnetic field orientation obtained by linearly polarised dust emission (Beuther et al. 2010). The blue segments represent the magnetic field orientation obtained by our linearly polarised methanol maser emission (Sect. 5.2); therefore the magnetic field follows the same direction indicated by the dust emission. The red and blue ellipses show the beams of SMA (1.65″ × 1.05″, position angle 51°) and MERLIN, respectively. Left panel: March; right panel: April.