(FOX40.COM) — Aerial surveys are underway at the site of the fatal Castle Peak avalanche as first responders attempt to recover the remains of disaster's the nine victims. The Nevada County Sheriff's Office is conducting flights "as needed," the department announced in a news release Friday. "Th e objective of the aerial surveys is to visually assess the conditions of the avalanche scene and snowpack as well as to make determinations if controlled avalanche mitigation may be possible at some point," Ashley Quadros, a spokesperson for the sheriff's office, said in a statement. If officials determine that mitigation is possible, first responders could deploy pre-planned explosives to intentionally release the unstable snowpack. A search and rescue team is seen responding to an avalanche disaster. (Nevada County Sheriff's Office) "These proactive measures are designed to reduce the risk of naturally occurring avalanches and enhance first responder safety within the affected area, so they may recover victims with lower risk," Quadros said. There are eight known fatalities who died in the avalanche, and a ninth person is missing but presumed dead. Efforts to recover their bodies have been hampered by adverse weather conditions and the risk of another avalanche. Read more: ‘Heartbroken’: Castle Peak avalanche victims’ families release statement If avalanche mitigation is necessary, the public will be notified in advance, Quadros said. Tahoe National Forest has closed the Castle Peak area to the public for the next month, and officials said it is crucial for unauthorized individuals to stay out of the area. The aerial survey involves several agencies, including the California Highway Patrol Air Operations, Placer County Sheriff's Tahoe Nordic Search and Rescue and the California Avalanche Center. On Tuesday, 15 backcountry skiers were caught in a deadly avalanche. The group, led by four people from Blackbird Mountain Guides, was returning from a three-day trip to Frog Lake Huts near Castle Peak when disaster struck at about 11:30 a.m. Six skiers — one man and five women — survived the avalanche and were rescued late Tuesday night, officials said. Six of the nine victims have been publicly identified. The backcountry skiers were “passionate, skilled skiers” who lived in the Bay Area, Idaho and the Truckee-Tahoe region, according to a statement issued Thursday by a local communications firm. ...read more read less