The pp pi system whose quantum numbers may assume values that are forb
idden for the NN system is investigated for the first time in the reac
tion pp --> pp pi(-)pi(+). The experiment was performed at ITEP (Mosco
w). The invariant-mass distribution of the pp pi(-) system reveals a r
esonance enhancement at M approximate to 2.06 GeV with a width about 1
0 MeV. The observed enhancement may signal the formation of a resonanc
e state predicted by quark models and required for interpreting data o
n low-energy pion-nucleus scattering accompanied by double charge exch
ange.