Exclusive measurements of the reactions $pdto$ $^3He pi^+ pi^-$ and $pdto$ $^3He pi^0pi^0$ have been carried out at $T_p=0.895$ GeV at the CELSIUS storage ring using the WASA detector. The $pi^+pi^-$ channel evidences a pronounced enhancement at low invariant $pipi$ masses - as anticipated from previous inclusive measurements of the ABC effect. This enhancement is seen to be even much larger in the isoscalar $pi^0pi^0$ channel. The differential distributions prove this enhancement to be of scalar-isoscalar nature. $DeltaDelta$ calculations give a good description of the data, if a boundstate condition is imposed for the intermediate $DeltaDelta$ system.
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