[O I] 630.0 nm, Hα, Ca II and Pa-13–16, and [Fe II] 1643.5 nm regions shown for S1–S5-A. For clarity, the [Fe II] 1643.5 nm region is enhanced. The confirmed MYSOs are boldfaced. We indicate the positions of the transitions with the red dashed lines (shifted with 260 km s⁻¹ with respect to the heliocentric frame). The Paschen series and Br-8 lines are marked by yellow dash-dotted lines for clarification. The center of Hα is saturated due to nebular emission and was clipped. All narrow features are either telluric lines or residuals from the nebular or sky subtractions.