Due to the paucity of detailed information and the lack of surviving meteorites or other physical evidence, researchers have also been unable to definitively state the exact nature of the dramatic event, even examining the possible occurrence of severe hail. Kevin Yau of NASA's Jet Propulsion Laboratory and his collaborators have noted several similarities of the Ch'ing-yang event to the Tunguska air burst in 1908, which, if it had occurred above a populated area, could have produced many fatalities.