[en] Using about 3 fb^-1 of data collected with the CLEO II detector at the Cornell Electron Storage Ring, CESR, on and just below the Υ(4s) resonance, the authors have looked for evidence of B mesons decaying into the charmed strange baryon Ξ_c. They present the first observation of B mesons decaying into Ξ_c⁰ and Ξ_c⁺, with Ξ_c⁰→Ξ^-π⁺, and Ξ_c⁺→Ξ^-π⁺π⁺