  The $\gamma\gamma\to\rho^0\rho^0\to 4 \pi$ reaction shows a broad peak at 1.5
GeV in the $(J^P,J_z)=(2^+,2)$ channel which has no counterpart in the
$\rho^+\rho^-$ channel. This "resonance" is considered as a candidate for a
$qq\bar q\bar q$ state in the "s-channel". We show, however, that it can also
be explained by potential scattering of $\rho^0\rho^0$ via the $\sigma$-
exchange in the "t-channel".
