Preliminary results of the analysis of the pppi- system produced in th
e reaction pp-->pppi-pi+ reveal a resonance with a mass M almost-equal
-to 2.06 GeV and a width < 15 MeV. The mass spectrum of the system ppp
i-, which can have any quantum numbers, including those forbidden in t
he np system, has been investigated for the first time. The observed r
esonance in the pppi- mass spectrum is in agreement with the quark mod
els. and it confirms the recently proposed explanation of the peculiar
features in the low-energy pionic double charge exchange on nuclei.