More than 580 people dead and over 2,400 missing after the flash flood disaster that struck on Wednesday.Nepal and China have resumed rescue efforts for survivors of the devastating flash flood that hit the border region two days ago, following a brief suspension as a “barrier lake” formed during the disaster began to overflow.Chinese rescue teams and vehicles were forced to pull back to safe ground, state broadcaster CCTV reported, as the risk of the lake bursting rose. Nepalese authorities also paused search operations for 90 minutes, an army officer confirmed on Friday.“As the risk posed by the upstream dammed lake was deemed manageable, rescue operations for the Gyirong mudslide disaster quickly resumed and were stepped up,” CCTV said.Nepal’s army spokesperson said the rise in water level comprised just 0.6 metres (2 feet).Rescuers earlier feared the “barrier lake”, formed as Wednesday’s flash flood carried huge volumes of mud and debris down a steep valley, could unleash another huge and destructive wave.In Nepal’s Rasuwa district, on the border with Tibet, residents were seen scrambling up hillsides to escape potential surges in the river level, according to the Reuters news agency.The barrier lake adds a new threat to communities devastated by Wednesday’s flash flood [EPA]The disaster unfolded as a glacier collapsed and sent a huge torrent of ice, water, rock, and mud down Himalayan river valleys, burying entire villages and destroying roads, bridges, and hydropower plants.In its wake, leftover debris trapped water to form a barrier lake, a natural dam created when landslides block a river.With water continuing to pour into the lake, the threat to downstream communities of another wave of flooding rose. China deployed an engineering team to conduct aerial surveys and 3D modelling of the site.By Friday afternoon, however, the secondary flood scare was confirmed to be “nowhere near” the magnitude of Wednesday’s disaster, said David Fisher, the delegation head for the Nepal International Federation of Red Cross and Red Crescent Societies (IFRC).The lake overflow added to “ongoing terror” rocking communities who have lost their homes, finding refuge in schools and government buildings, Fisher told Al Jazeera.“It’s an extremely difficult time,” he added.Relief supplies blockedThe death toll from the disaster continues to rise. On Friday, Nepal’s disaster authority reported at least 579 deaths, with 1,924 people missing.Chinese authorities reported on Friday that the death toll in Tibet has now risen to at least five, with 558 people missing.Bishal Nath Upreti, president of the Nepal Centre for Disaster Management, told Al Jazeera that conditions are “extremely difficult” for those trapped in the disaster zone, as destroyed roads have left them completely cut off.Nepal’s disaster authority said a total of 4,451 people had been rescued as of Friday, with 16 helicopters carrying out 99 rescue flights so far.Al Jazeera’s Katrina Yu, reporting from Beijing, said the number of missing is expected to rise. China has deployed about 500 military and paramilitary personnel and sent Premier Li Qiang to supervise operations on the ground, while Nepal has deployed 30,000 security personnel to search remote, cut-off valleys, she said.More ⁠than ⁠90,000 people are estimated to have been affected ⁠by disaster, the ⁠IRFC’s Fisher said on Friday.Teams have been unable to reach some of the hardest-hit areas in Rasuwa, which remains accessible only via helicopter.“We’re very concerned for them,” Fisher said.