Robbins, a self-help guru and motivational speaker, asked some of the 6,000 people who attended his seminar at the San Jose Convention center to walk across one of 12 lanes of "hot coals" set up outside.
A 25-year old college student said he heard "wails of pain, screams of agony" from participants in the firewalk, the newspaper reported. "It was horrific."
Robbins's Web site promotes "The Firewalk Experience," in which people walk across coals ranging in temperature from 1,200 to 2,000 degrees Farenheit, the newspaper reported.
Fire officials said emergency responders treated 21 people for burns at the scene, and more 911 calls from people in area hotels, the newspaper reported.
Officials from the San Jose Fire Department say they "discourage" people from walking over hot coals.