Authorities have started handing over remains of the victims of one of India’s worst aviation disasters after identifying some through DNA tests.

While the official investigation is ongoing, preliminary video footage and expert reviews have highlighted several main theories.

According to the International Civil Aviation Organisation, audio recordings from cockpit voice recorders supplement flight data by providing related details on flight crew responses. The recordings also aid in assessments of how radio communications or other outside distractions may have been a factor in an accident.