It is now being reported that the avalanche occurred in the biggest avalanche area on Berthoud Pass, the Stanley Run. It is located on the east side of Berthoud Pass, just south the top of the pass.
Apparently CDOT has been doing control work in the area through the storms and was last done on Wednesday. This morning the conditions were fine, but there was a lot of wind that has come up and depositing snow in those avalanche runs and this may be the cause.
This is all from the spokesman from the Colorado Avalanche Information Center.