Two small planes collide in midair near Denver, three dead

Three people were killed on Saturday when two small planes collided in midair over Boulder County, Colorado, crashing into an open field and leaving two separate crash sites, local authorities said.

Shortly before 9 a.m. local time, police "received multiple emergency phone calls" from witnesses who saw the two aircraft collide about 30 miles north of Denver, the Boulder County Sheriff's Office said in a statement.

When first responders came across the first crash site, both people onboard the plane were dead, police said. The pilot of the second downed plane, who was the sole occupant, also was dead when emergency crews reached the wreckage, the sheriff's office said.

None of the victims were immediately identified.

The two aircraft were a Cessna 172 and a Sonex Xenos, the National Transportation Safety Board said in a statement, adding that investigators are probing what led up to the accident.

The Sonex Xenos is a lightweight aluminum, homebuilt aircraft, according to the company's website. The Cessna 172 Skyhawk is a single-engine airplane that seats four.

The Federal Aviation Administration said in a statement that the planes collided near the Vance Brand Airport, a general aviation airport in Longmont, Colorado.