The inaccessibility of the Germanwings Flight 9525 crash site has made it difficult for authorities to recover what remains of the plane and the 150 passengers who died when the plane collided with the French Alps on Tuesday. Crew members rely on helicopters, climbing gear and local mountaineers to access the remote area in Seyne-les-Alpes, France, and uncover what evidence remains.

French authorities work during daylight hours to find pieces of the Airbus A320, most of which are no bigger than a car door, the Associated Press reported. Flight 9525 crashed at such a high rate of speed that investigators have relied on DNA testing and an on-site database to identify victims’ remains.

“We have not found a single body intact,” French forensic investigator Col. Patrick Touron said Friday, the AP reported. “DNA will be the determining element that will lead to identification.”

Workers have reportedly uncovered between 400 and 600 “biological elements” at the crash site, which were subject to immediate testing before further degradation could occur. Family members of the deceased have given authorities victims’ toothbrushes and DNA samples to aid positive identification of victims. Dental files and jewelry were also examined to facilitate the process.

Recovery efforts can proceed only as weather allows and are expected to go on for weeks. Authorities have yet to find the plane’s second black box, which could provide investigators with further information on the events that preceded the crash.

Flight 9525 co-pilot Andreas Lubitz, a 27-year-old native of Montabaur, Germany, locked the flight commander out of the cockpit and deliberately altered the plane’s course so it would crash into the French Alps, Prosecutor Brice Robin of Marseille, France, said at a news conference Thursday. An analysis of the plane’s first black box, a cockpit voice recorder, revealed the flight commander tried, without success, to break down the cockpit door to regain access to the plane’s controls.

Attempts to ascertain possible motives for Lubitz’s alleged actions are ongoing. German airline Lufthansa, which owns Germanwings, has offered financial compensation of up to 50,000 euros (US$54,000) to relatives of Flight 9525’s victims.