GRAND JUNCTION, Colo. - One boy is dead and another has been airlifted to a hospital in Aurora Tuesday night as Mesa County deputies investigate what happened.

"Our local dispatch received a call of two children needing immediate assistance up on the Grand Mesa, sheriff’s spokeswoman Heather Benjamin told 7NEWS.  "Ultimately,  what occurred was a small child died and 4-year-old child was transported by CareLife to St Mary's Hospital and then transferred to The Children's Hospital (in Aurora)."

Benjamin said the incident occurred on Powderhorn Road, near the ski resort, but not at the ski resort.

7NEWS listened to police radio traffic from the incident that indicated exposure to carbon monoxide may have been a factor, but that was not confirmed by Benjamin.

"We're not speculating on our case at this point," Benjamin said. "We have a death investigation. Our investigators are working very hard on this."

KKCO TV talked to the grandfather of the two boys. Robert Mathena identified the dead boy as 2-year-old William Jensen. The grandfather said William’s four-year-old brother, Tyler,  was airlifted to The Children’s Hospital in Aurora where he has been placed on life-support, the station reported.

"I don't have any information about who was with the children," Benjamin told 7NEWS. "Interviews that were done by our investigators are not something we will release at this point. We have not arrested anyone. This remains a death investigation at this time."

Investigators are waiting for an autopsy to confirm the cause of William's death.

The boys' mother, Heather Jensen,  posted a photo of her sons early Wednesday morning on her Facebook page. The boys' father died in a car accident in Rifle last month, KKCO reported.