St. Paul typically issues about 400 permits a year for school and other groups to explore a part of the park where numerous fossils are embedded in the Mississippi River bluff.

St. Paul authorities shut down a popular fossil-hunting area in a riverside park Thursday, one day after two children were killed and two others injured by a landslide.

Mayor Chris Coleman announced the indefinite closure after searchers late Thursday morning recovered the body of a boy who had been missing since rain-saturated soil gave way the afternoon before. The boy, who family members identified as 10-year-old Mohamed Fofana, was on a field trip to Lilydale Regional Park with other fourth-graders from Peter Hobart Elementary School in St. Louis Park.

Another boy, who authorities identified as 9-year-old Haysem Sani, died at a hospital Wednesday after being pulled from the soil and sand.

"You think about the joy those children were experiencing. The quickness in which that tragedy struck, it is really unspeakable in its nature," Coleman said.

St. Paul typically issues about 400 permits a year for school and other groups to explore a part of the park where numerous fossils are embedded in the Mississippi River bluff.

"It's a wonderful part of our city, a wonderful part of the Mississippi River valley and an exciting place to be," Coleman said. "But at the same time, it's a wild area."

The city requires permits for fossil hunting and requires applicants to sign a waiver releasing the city from any liability for injuries or property damage. The waiver states that "some of the conditions and locations within the Lilydale Regional Park area are hazardous to persons or property" and that park users must assume all liability "due to its unsafe conditions."

The permit form also says those signing on behalf of a group certify that they have made those conditions known to all participants or their parents or guardians in the case of minors.

Peter Hobart Elementary Principal Shelley Nielsen and the school district's superintendent, Debra Bowers, declined during a brief news conference to answer questions about whether parents had been notified of potential hazards. Bowers said she had no information on whether anyone called ahead to see if conditions were safe.

The flag flew at half-staff outside the school Thursday as the officials spoke in front of a memorial made up of a couple dozen or so bouquets, more than a dozen stuffed animals and several balloons in the district colors of orange and black tied to a fence. One pink, heart-shaped card said "R.I.P." and bore the signatures of several children.

Bowers called it "an incredibly sad day for our schools and our entire school community."

Nielsen described the boys as "outstanding students" with a love of life and learning and "very engaged parents."

Assistant Fire Chief Jim Smith told reporters he arrived Wednesday to find 20 to 30 people attempting to rescue the children. He described a horseshoe-shaped pit 30 to 40 feet deep, and "a very dangerous situation facing all rescuers" with lots of loose soil and water running off.

The boys were hit by 4 to 5 feet of soil and rock, he said.

Two boys were pulled from the soil and sand — one buried to the waist and the other completely buried. One of them was Haysem, the 9-year-old, who died at Regions Hospital. The other, whose name was not released, was in serious condition Thursday at that hospital.

A third child, also not identified by authorities, was treated for minor injuries and released.

Smith said that given the time it took to move many tons of material, it soon became clear that the search for the fourth child, later identified as 10-year-old Mohamed, was a recovery effort. The dangerous conditions led to suspension of the search Wednesday night until the weather improved Thursday morning.

Parks spokesman Brad Meyer said signs and barricades went up Thursday afternoon to cordon off the 35 closed acres in the 384-acre park. He said fossil-hunting permits will be suspended for at least two weeks, but the length of the closure will depend on the outcome of an investigation into the accident.

"There's going to be a full review and assessment of what happened," Meyer said. "That will take as long as we need to get it right."

Mohamed's father, Lancine Fofana, told the St. Paul Pioneer Press his son had been looking forward to the field trip.

"He came to me and said, 'You know we have a field trip tomorrow? I'm so happy,'" the father said.