Two other children were sent to a hospital with injuries and a firefighter was hurt when he was hit in the head by a rock while taking part in the rescue efforts Wednesday, the St. Paul Pioneer Press reported.
The slide occurred in Lilydale Regional Park where students from two fourth-grade classes at Peter Hobart Elementary School in St. Louis Park were on a field trip.
St. Paul Fire Department spokesman Steve Zaccard said the water-saturated soil endangered the dozens of emergency responders who converged on the scene for the rescue effort.
"Now it's too dangerous to continue even that effort because of the water flowing into the hole" the children were trapped in, Zaccard said.
St. Paul firefighters and police officers dug with their bare hands to free the children, the Pioneer Press said.
One student trapped in mud up to his waist was freed after about an hour and it was an hour and a half before a child who was later pronounced dead at Regions Hospital was extricated, the newspaper said.
"This is tough on the rescuers," Zaccard said. "It's young children just here to have a good time
"This will become a recovery effort."