Fire officials said the injured included children and adults.
Nine teenagers were taken to IU Health Methodist Hospital, including one in critical condition. Three of those were treated and released, hospital spokeswoman Sally Winter said. She said 10 others, including nine teenagers and a toddler, were taken to Riley Hospital for Children. Seven of those teenagers were treated and released, Winter said.
Many of the patients were suffering head, arm and leg injuries, fire officials said.
Roads near the scene were closed, and authorities urged people to use caution in the area. A hazardous materials crew was cleaning up diesel fuel that spilled in the crash.
Outside the church, a yellow school bus with the church school's name was parked outside with piles of sleeping bags and suitcases nearby. Families hugged outside and talked quietly before going inside, where they met with Ballard and Riggs Saturday evening.
Ballard described the families as "remarkably positive" despite their sorrow.
"Some of the teenagers are hurting pretty bad and you can see that in their faces," he said.
Church member Jeff Leffew, 44, of Fishers, who had three daughters on the bus that crashed and a fourth on a second bus, said he was waiting to pick them up in the church parking lot when the second bus arrived. He said he knew immediately that something was wrong because the kids on the bus were screaming.
He went to the crash scene and found his three daughters with only bumps and bruises.
He called the crash scene "surreal."
"You're just praying that it's not as bad as it looks," he said.
Associated Press writer Tom Murphy contributed to this story.