Investigators trying to figure out why rocks tumbled down on concert-goers at Red Rocks Amphitheater early Sunday found no explanation.
“We may never know,” said Arts & Venues Denver spokeswoman Kristin Rust.
Investigators looking at Creation Rock found no loose rocks or instability, and no changes from a November 2008 assessment of the formation.
Creation Rock is one of the two rock formations that form the amphitheater. Geologists estimate 300-foot-tall sandstone formation to be more than 290 million years old.
At the base of Creation Rock, on the north side of the amphitheater, seven people were struck by a dozen or more falling rocks at about 1 a.m. Sunday, as Sound Tribe Sector 9 played its last encore. The electronic-funk jam band played two sold-out shows this weekend.
Authorities received unconfirmed reports of people climbing on the rocks in that area — a violation that can result in a $999 fine.
Rust said extra security will monitor the rock face the rest of the year “in the event that it was caused by climbers.”
At least a half dozen rocks fell on people who were on the north stairway, approximately between rows 20 and 40.
Four people were taken to hospitals.
Among them was Jennifer Ackerman, a 34-year-old mother of two who was at the concert with her cousins.
Her sister-in-law, Kelly Ackerman, said today that Jennifer suffered a head injury and is still undergoing tests. She also has a fractured eye socket and sinus and chipped teeth.
Kelly Ackerman said the women saw people climbing on the rocks before the rocks fell on them.
The names and conditions of the other people injured weren’t immediately available.
Sara Burnett: 303-954-1661 or sburnett@denverpost.com
