Three Oklahoma City middle school students are safe after being trapped under an elevator at school, but a newly released 911 call gives a glimpse into what one of the young girls called an “agonizing” experience.

“Oh my God. We’re trapped under an elevator,” a girl’s voice can be heard saying in the 911 call. In the background can be heard high-pitched screams from her friends yelling “Please help us. Now.”

The two seventh-graders and one sixth-grader from the Classen School for Advanced Studies spent about 40 minutes trapped under the 500-pound elevator on Tuesday before being rescued. They lay on their backs and struggled to breathe with less than a foot of space between the bottom of the elevator and the ground.

One of the girls, 12-year-old Ambri Tygard, credits her friend’s combat boots with saving their lives.

“[The elevator] came down right on her boot and stopped it,” Tygard told ABC News’ Oklahoma City affiliate KOCO.

However, Oklahoma City elevator inspector Jim Burrell who is familiar with the type of small, limited-use access elevator in the school, said the elevator may have just stopped on its own.

Burrell has not yet inspected the elevator but told ABCNews.com, “The faster the elevator, the deeper the pit. This one has a real shallow pit, about eight inches.” The pit is the amount of space between the bottom of the elevator and the ground, where elevators automatically stop.

So the elevator may have come to an automatic, albeit life-saving, stop without the help of the boots.

Tygard said that she and her friends were on the first floor of their school when they decided to take the elevator.

“I didn’t think it was unsafe or anything. I just thought it was normal, until I looked up [and] realized, ‘This isn’t the elevator. This is the shaft room,’” Tygard told KOCO.

But by the time Tygard had made this realization, it was too late because her friend has already closed the door and they were locked inside.

Tygard said that within 30 seconds, the elevator that was three floors above them, came down and was right above them.

“I was like, ‘We’re going to die. We have to find a way out. There must be some way out,’” Tygard said.

The girls were rescued about 40 minutes later and taken out of the school on stretchers by paramedics. They suffered only minor injuries.

Three Oklahoma City girls were trapped under an elevator at their school, Nov. 15th, 2011. (Photo credit: ABC News)

Tierney Cook-Tinnin, a spokeswoman for Oklahoma City Public Schools, told ABCNews.com that the school’s principal said that the elevator is only used by students who are injured or handicapped and that the door to the elevator is always locked.

School officials are still investigating exactly how the incident happened. The school’s principal has interviewed a couple of the students, but since Tygard is still in the hospital, they have not spoken to all three girls yet.

“Until we’re able to talk to all of them involved in the same room, we don’t want to speculate,” Cook-Tinnin said.

For now, Tygard is focusing on recovering and getting back to school. She is still having trouble walking, but doctors told KOCO that she should be walking in a few days with physical therapy and hopefully back to school next week.