Six people were hurt – two critically – when part of a heating and ventilation system collapsed at a resort pool in Colorado on Saturday. There were 50 to 100 guests in the pool when the collapse occurred about 9:50 a.m. at the Gaylord Rockies resort near Denver International Airport, Aurora Fire Rescue said.

Large metal ductwork and mechanical parts that were mounted on the ceiling crashed down upon the pool deck and into the water, covering nearly the entire area of the pool, agency spokeswoman Sherri-Jo Stowell said.

The victims suffered injuries that ranged from penetrating wounds and cuts to “injuries consistent with being crushed,” she said. She declined to release ages of the victims, citing department policy.

Fire Chief Alec Oughton said crews were already at the resort, running up and down its stairs for physical training, when the collapse happened.

The resort will be conducting an investigation into the cause of the collapse and will be responsible for keeping guests out of the pool area, Oughton said.

The resort and convention centre has more than 1,000 rooms, a water park and meeting spaces.

“Our hearts go out to all those who were injured today, to their families and to those traumatized by witnessing what occurred,” city spokesman Ryan S. Luby said in a statement.