Story highlights An explosion at a Civil War re-enactment sends three children to the hospital

Spark from fired cannon sets off additional charges

Witnesses say two of the children were engulfed in flames

What was supposed to be a celebratory lesson in American history has sent three children to the hospital.

They were a part of a Civil War re-enactment group watching a parade in Orem, Utah, when a cannon set off an explosion Saturday. Witnesses said two of the three children injured were initially engulfed in flames, according to CNN affiliate KUTV.

"When the flames went up in the air these three children started crying. One little girl's clothes were on fire, we're told," witness Brittany Tait told KUTV. "People were running with water to douse her."

The blast happened at the start of the parade, the city's Department of Public Safety said.

The cannon was fired, and a spark landed on a pouch containing additional charges for the cannon. The smoldering ember set off the contents of the pouch, blowing it up and injuring all three children, the press release explained.

The extent of the children's injuries was not immediately known Sunday, but authorities said they were in stable condition when they were transported to a nearby hospital.