  We present the results of a closure phase analysis of 3 mm very long baseline
interferometry (VLBI) measurements performed on Sagittarius A* (Sgr A*). We
have analyzed observations made in May 2015 using the Very Long Baseline Array,
the Robert C. Byrd Green Bank Telescope and the Large Millimeter Telescope
Alfonso Serrano and obtained non-zero closure phase measurements on several
station triangles - indicative of a non-point-symmetric source structure. The
data are fitted with an asymmetric source structure model in Sgr A*,
represented by a simple two-component model, which favours a fainter component
due East of the main source. This result is discussed in light of a scattering
screen with substructure or an intrinsically asymmetric source.
