For additional coverage see CNN affiliate KMGH.
(CNN) -- A helicopter carrying four people crashed Friday morning on Colorado's Pikes Peak, authorities said.
Rescue crews took one person to the hospital by helicopter and three others by ambulance, but their conditions were not immediately known, said Teresa Murphy of the El Paso County Sheriff's Department.
It was not clear what caused the crash, which happened in clear weather, she said.
The helicopter was filming a commercial for Audi, Murphy said. It went down around 7:30 a.m. about a mile below the 14,110-foot summit, said Lt. Lari Sevene.
In a statement, Audi said the crew was filming a test run of the "Autonomous Audi TTS Pikes Peak," a program among Audi, the Electronic Research Laboratory in Palo Alto, California, and Stanford University.
Its goal involves driving up Pikes Peak without a driver behind the wheel "to demonstrate the capabilities of advanced driver assistance systems and GPS," the statement said.
The car was not involved in the incident.
The research activities on Pikes Peak have been suspended, it said.
CNN's Dina Majoli contributed to this report.