The measurements on strong quasiparticle injection through a tunnel barrier into a high-${\mathit{T}}_{\mathit{c}}$ ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7}$ (YBCO) bicrystal film/junction or a YBCO film are presented. With an increase of tunnel injection current, both the Josephson and film critical currents decreased and were driven to zero to yield the normal state at a certain critical injection current density which ranged 20--140 A/${\mathrm{cm}}^{2}$ for 70 to a few 100 mV voltage bias. The results are qualitatively different from simple heating phenomenon and reflect nonthermal nature of high-${\mathit{T}}_{\mathit{c}}$ superconductors under injection.