In a search for emission line objects made in a southern region of M 33 using narrow band filters centered on [O III], Hα and adjacent continua, we detect some known and new objects that can be classified as planetary nebulae candidates (PNc). This search, the deepest one made up to now in M 33, has allowed us to detect 48 PNc, from which 14 have a ratio of [O III]-to-Hα fluxes greater than 1. We compare our findings with a previous search and present the list and finding charts of these interesting objects. Figures 3 to 11 are only available in electronic form at http://www.edpsciences.org