We have performed fully correlated calculations using as a basis set the cc-pV5Z expansion with geometry optimization for the O3H+ moiety and have then calculated the partial cuts of the potential energy surfaces (PESs) for the first two roots using the cc-pDZP basis set expansion. Two electronically induced conical intersections (CIs) were found in the C-s-plane subspaces and one of them was accurately located by calculating the geometric phases for different path integrals. We also discuss the adiabatic versus nonadiabatic effects and suggest a kinetic mechanism for the dynamics of the gas-phase protonation of ozone which includes the role played by the present conical intersections. We also try to provide useful suggestions for the practical search of conical intersections based on a physically guided subspace factorization. (C) 2000 American Institute of Physics. [S0021-9606(00)30611-0].