A day after four young rappelers were washed away in a flash flood at Qumran National Park, police said that they were still investigating whether negligence was to blame for the young adults' deaths. All four of the rappelers - Tal Alon, 24, from Moshav Mei-Ami; Dror Koren, 23, from Herzliya; Noa Shapira, 23, from Kfar Saba and Amit Gottleib, 23, from Rehovot - were buried Sunday, less than 24 hours after horrified park rangers, friends and bystanders saw the four swept away by a powerful surge of muddy water rushing down Nahal Qumran. One of the park rangers who was at the site, Ismail Abu Mahmoud, said Sunday that he had attempted to warn the youths of the danger as early as an hour before the floods started. Abu Mahmoud said that at 2:30 p.m., when the first drops of rain had begun to fall, he had gone to warn the group of 11 rappelers who had entered the wadi northwest of the Dead Sea. The park warden said he had yelled down to them about the danger, but that while some of the climbers had headed for safety, others had disregarded his instructions until it was too late. Abu Mahmoud's Sunday statement seemed to concur with an eyewitness account given to The Jerusalem Post hours after the tragedy. In that account, a photographer who was on the scene said that some of the climbers had disregarded both his warnings and those of the park ranger. But surviving members of the group, all experienced rappelers, said that they had not been adequately warned of the danger of the flash flood. Friends said Sunday that Dror Koren had been an experienced climber and an officer in the Home Front Command's elite Search and Rescue Unit. Members of the group said that as early as two weeks in advance, they had begun to compile safety information and weather reports for the Qumran area. Members of the group emphasized that when they had purchased the entry tickets to the park, nobody had warned them of the danger. At one point, when the group realized that they were trapped in the canyon, Koren called his older brother, Yaron, a firefighter, to tell him that they were in need of rescue. Yaron contacted another firefighter whose brother was also on the trip, and they and two co-workers set out to try to rescue the climbers - but to no avail. All four of the hikers who were killed were still attached to the rappelling lines when the torrent slammed into them.