BOULDER - 9NEWS has learned that five people are dead after a mid-air collision over Boulder where a plane hit a tow line that was pulling a glider.
Former NTSB investigator Greg Feith says four of the people who were killed were on a Cirrus plane that hit a tow cable that was behind another plane. That cable was pulling a glider.
At least one person on the tow plane was also killed.
Rick Brough with the Boulder County Sheriff's Office says the glider cut lose from the cable just before the crash and landed safely.
Feith says there are survivors, but it is not clear if any were on either of the planes.
The crash happened around 1:30 p.m. on Saturday.
Both planes went down in Boulder County open space, but the crash sites are separated from each other by a ridge. The debris field is over several miles and authorities are search for piece of the planes, including the sections of with the tail numbers on them.
Amateur video sent to 9NEWS shows something smoking with a parachute falling to the ground. Witnesses also report seeing fires on the ground in the area.
The video was taken by Hugh Walton of Boulder. His home is about a half mile from the crash site.
"I realized this is a plane with a person in it and I thought, 'Oh, that is not good,'" Walton told 9NEWS. "I was just leaving my neighborhood and I saw some riders, some cyclists, pull over to the side of the road and they were pointing and looking up. So I glanced over my shoulder and I saw some smoke and some flames going on way up in the sky."
Walton's wife says she heard a boom right above their house around the time of the crash.