An unidentified boy scout leaves the West Harrison High School in Mondamin, Iowa, where he was reunited Thursday with relatives. At least 4 died and at least 40 were injured when a tornado touched down Wednesday at the Little Sioux Scout Ranch. (Nati Harnik/Associated Press)

A tornado struck a boy scout camp in western Iowa on Wednesday, killing at least four people and injuring 40, according to officials and witnesses.

'The camp is virtually destroyed — there's nothing left in there.'— Lloyd Roitstein, Boy Scouts of America spokesman

Officials said the tornado touched down about 7 p.m. CT at the Little Sioux Scout Ranch, about 60 kilometres north of Omaha, Neb.

Iowa Homeland Security spokeswoman Julie Tack said there were 93 campers, ages 13 to 18, and 25 staff members at the camp.

All of the children had been accounted for late Wednesday, after rescuers cut their way through downed trees and debris to reach them, said Russ Lewrenson of the Mondamin Fire Department. Most of those hurt were on a hike when the storm hit.

"There had to be sawing and stuff to get to the scene," Lewrenson said.

The campers were on a week-long leadership training session, which was to end on Saturday, Lloyd Roitstein, spokesman for the Boy Scouts of America, told CNN from the scene.

"The camp is virtually destroyed — there's nothing left in there," Roitstein said.

The tornado touched down as Iowa's eastern half grappled with flooding in several of its major cities. The storm threatened to stretch Iowa's emergency response teams even further.

Tack said officials were confident that the state's emergency response teams could handle the crisis because western Iowa had been largely unaffected by the recent flooding.

With files from the Associated Press