By Jay Gormley, CBS 11 News

DALLAS (CBSDFW.COM) – An escalator that apparently malfunctioned left 18 students and two adults with injuries.  Some members of the injured group were on a field trip from Thompson Elementary School in Quinlan.

DART spokesman, Mark Ball says the students were on the down escalator at Mockingbird Station in Dallas when it suddenly sped up.  The students and adults were thrust forward and fell to the bottom of the escalator.

The students had just performed as a choir at Zion Lutheran Church in North Dallas, and were on their way to a museum when the accident abruptly cut the day short.

According to Ball, of the 20 injuries, eight middle school students with minor injuries were sent to Children’s Medical Center.  Hospital spokeswoman Laurie Holloway says the injuries were not severe.  “Most of the injuries were minor. Scrapes, bumps and bruises.”

Ball says one child is believed to have a broken leg.  All 8 of the injured children have since been released from the hospital.

The two adults were sent to Parkland Hospital with minor injuries.  Those treated at the scene were put on a bus that went back to Quinlan.

Witnesses says someone hit the emergency stop button, but engineers are inspecting the escalator to officially determine what went wrong.  DART says an inspection in April found no problems with the escalator.