CNN — A field trip turned tragic for a group of fourth-graders in Minnesota when gravel drenched by rain gave way, killing one child and injuring two others. A fourth child remains missing.
Crews worked late into the night Wednesday at Lilydale Regional Park, washing away soil with fire hoses and bringing in search dogs to look for the missing child.
They will resume their search for the child's body Thursday morning.
"Such an unbelievably tragic situation at #lilydale," St. Paul Mayor Chris Coleman tweeted Wednesday evening.
"My heart goes out to the kids and families. First responders still working feverishly."
The children were students at Peter Hobart Elementary School who were at the park by the Mississippi River on a field trip.
Neighbors told CNN affiliate KARE that students often go to the area to look for fossils. There have been been occasions, they said, where parts of the ground moved or collapsed because of the wet conditions.
"It appears they were walking along in the ground (and) after the rain we've had, it was so soft and it gave way," St. Paul Fire Marshal Steve Zaccard told reporters. "They fell into what became a hole and the earth came on top of them."
Crews began a frantic search, digging with their shovels and hands to reach the children.
"They grabbed shovels out of the shed and they said that they needed shovels," resident Sue Zoccoli told CNN affiliate KARE.
The first child was pulled out quickly. But it took crews more than an hour to reach the second who was half submerged in water, reported affiliate WCCO.
"That's when they uncovered the hand of the third who later died," Zaccard said.
So far, they have found no signs of the fourth child.
Two firefighters suffered minor injuries during the rescue: one was struck on the head by a rock; the other received a back injury.
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