The results of resonance searches in {\Xi }^- \pi ^-, {\Xi }^- \pi ⁺, \overline {\Xi }⁺\pi ^- and \overline {\Xi }⁺\pi ⁺ invariant mass spectra in proton-proton collisions at \sqrt {s}=17.2 GeV are presented. A narrow state was observed in {\Xi }^- \pi ^- spectra with mass of 1.862 \pm 0.002 GeV/c² and width below the detector resolution of about 0.018 GeV/c². This state is identified as a candidate for the hypothesized exotic { \Xi }₅^-- baryon with S = -2, I = {3}/{2} and a quark content of (dsds\bar {u}). {\Xi }^-\pi ⁺ and the corresponding antiparticle spectra show an indication of enhancements at the same mass. Very preliminary results of resonance search in p K_S⁰ channel show a resonant structure at 1.526 GeV/c².

PACS numbers: 14.20.Jn, 13.75.Cs, 12.39.--x