(NBC Dallas) - The event was part of a three-day series called "Unleash the Power Within," according to the motivational speaker's website.

More than 30 people attending a Tony Robbins event in Dallas have been treated for burns after the motivational speaker encouraged them to walk on hot coals, firefighters said.

Dallas Fire-Rescue spokesman Jason Evans said multiple units responded to the Kay Bailey Hutchison Convention Center to treat an unknown number of "burn victims" just after 11 p.m. Thursday.

Several people suffered burns to their feet and lower extremities after trying to walk across hot coals at a seminar hosted by Robbins. According to his website, the event was part of a three-day series called "Unleash the Power Within" meant to "help you break through any limit and create the quality of life you desire."

A Dallas Area Rapid Transit bus was requested to help hold some of the 30 to 40 people being evaluated. The severity of their injuries was unclear, but Evans said only about five people chose to be hospitalized.

Representatives for Robbins didn't immediately return messages Friday.

More than 20 people were treated for foot burns after a similar Robbins event in 2012 in San Jose, California.