But some clashes did occur. Excess crowds, estimated at 50,000, who had been unable to obtain tickets filled an adjacent hillside, and the weekend was marred by disturbances, including fence crashing and crowd surging, during the most popular performances. Saturday evening's disturbances were particularly significant, prompting producer George Wein, who feared a riot, to announce that the Sunday evening Led Zeppelin appearance was cancelled. That show was allowed to go forward as initially scheduled after much of the overflow crowd had left the city, following the cancellation announcement.