Other source:
As the dust clears, Cell's mangled body becomes visible. While the rest of the Z fighters believe that they've won, Goku thinks differently. He senses that something isn't right when he can still feel a large amount of energy is what's left of Cell's body. Suddenly, Cell's body stands up, to the horror of virtually everybody, and regenerates the missing parts. Cell's energy has been depleted by the attack, but Goku's energy has been depleted more severely, and as the battle continues, it becomes clear that Goku is no match for Cell. Knowing that he cannot win, he declares that Cell is the winner. The Z fighters, and Cell, can't believe it.
