  Debris discs represent the last stages of planet formation and as such are
expected to be depleted of primordial gas. Nonetheless, in the last few years
the presence of cold gas has been reported in $\sim$ 20 debris discs from
far-IR to (sub-)mm observations and hot gas has been observed in the optical
spectra of debris discs for decades. While the origin of this gas is still
uncertain, most evidences point towards a secondary origin, as a result of
collisions and evaporation of small bodies in the disc. In this paper, we
present ALMA observations aimed at the detection of CO gas in a sample of 8
debris discs with optical gas detections. We report the detection of CO
($^{12}$CO and $^{13}$CO) gas in HD 36546, the brightest and youngest disc in
our sample, and provide upper limits to the presence of gas in the remaining
seven discs.
