A Dalitz plot analysis of decays is performed using data samples of pp collisions collected with the detector at centre-of-mass energies of and , corresponding to a total integrated luminosity of . A satisfactory description of the data is obtained when including a contribution representing an exotic resonant state. The significance of this exotic resonance is more than three standard deviations, while its mass and width are and , respectively. The spin-parity assignments and are both consistent with the data. In addition, the first measurement of the branching fraction is performed and gives where the first uncertainty is statistical, the second systematic, and the third is due to limited knowledge of external branching fractions.