California prison officials have halted an experiment aimed at trying to force prison gangs to get along.

Officials say the temporary cutoff came after the inmates ended up fighting and even rioting when they were allowed to be in the recreation yard together.

The effort was started more than a year ago when officials would allow prisoners of different gangs into the rec yard to quote "make peace." But gang members at several state prisons took part in what critics are calling "gladiator fights" that they allege prison officials deliberately set up.

Prison officials have denied those allegations.