As a school chaperon spoke to emergency dispatchers after "an avalanche of sand" buried several students during a field trip to a St. Paul park, she stopped to comfort an injured fourth-grader.

"Stay calm, Devon. Devon, you're alive. You're fine. Devon, you're fine. I got you, Devon," the woman on the phone said.

"OK, we're sending help there, ma'am, hold on," the dispatcher said.

"Thank you."

"Shh. I got you, Devon, you're fine, you're fine,'' the woman continued. "You're alive, Devon. You just got a little bit of owie."

Fourth-grade students from Peter Hobart Elementary School in St. Louis Park had been on a fossil-hunting field trip at Lilydale Regional Park on the bluffs of the Mississippi River on May 22 when the hillside gave way.

Frantic 911 callers tried to describe the collapse of this cliff.

Mohamed Fofana, 10, and Haysem Sani, 9, were killed. Two other students, identified by the school as Lucas Lee and Devon Meldahl, were injured.

According to 911 transcripts from two calls that were released Wednesday, it was hard to describe exactly what had gone wrong.

"We heard a loud noise. I was at the top of the hill, but I'm afraid that if something came down, the noise of the cliff, I can't, I can't even tell you what I'm thinking is happening," another female caller told a dispatcher.

"Ma'am. Well, I need to have an idea of what happen so I send the right help," the dispatcher said.

"It's OK, well, I think there's a giant, a cliff on the other side of us so I can't see it. It collapsed," the caller put simply.

"OK."

"And the kids are telling me a boy is under the rock."

Both callers told dispatchers that the two classes had been climbing up toward the top of the bluff when the landslide occurred.

Frantic emergency crews used shovels and even their bare hands to dig Haysem's body from the ground within hours of the slide. However, nightfall and dangerous conditions made workers postpone the rest of the search until the next day. Mohamed's body was found the next morning.

Following the landslide, the city closed access to the fossil grounds, a popular field trip destination, until further notice. The city also hired a civil ­engineering firm with geotechnical ­expertise to examine the site.

Nicole Norfleet • 612-673-4495 Twitter: @stribnorfleet