SAN JOSE, Calif. >> Fire officials in California say at least 21 people were treated for burns after attendees of an event for motivational speaker Tony Robbins tried to walk on hot coals.

The San Jose Mercury News reports that at least three people went to a hospital and most suffered second- or third-degree burns.

Robbins was hosting a 4-day gathering called “Unleash the Power Within” at the San Jose Convention Center. Witnesses say on Thursday, a crowd went to a park where 12 lanes of hot coals were on the grass.

Robbins’ website promotes “The Firewalk Experience” in which people walk on super-heated coals.

Witness Jonathan Correll says he heard “screams of agony.”

Fire Capt. Reggie Williams says organizers had an open fire permit and emergency personnel were on standby.