Authorities on Aug. 27 said several Americans had been rescued while dozens more remained missing among the now more than 1,000 people unaccounted for after deadly flash floods struck Nepal less than 24 hours earlier.The flash floods took place at about 8:30 a.m. local time in the Bhotehoski and Trishuli rivers in the Himalayan country's northern Rasuwa district near China's Tibet border, the Nepal Tourism Board reported.The catastrophic deluge affected riverine areas in Nuwakot, Dhading, Gorkha and other districts, leaving homes, buildings, roads and bridges destroyed and hundreds dead, according to information from the tourism board and the U.S. State Department.In an updated statement on social media, Nepal's tourism board said that the National Disaster Risk Reduction and Management Authority reported that 31 foreign tourists, including two U.S. citizens − a 52-year-old woman and a 55-year-old man − were rescued from the Timure and Bhotehoski area of Rasuwa.Search and rescue operations remained underway in the country as well as part of neighboring China for 667 missing travelers, including 127 Nepalese nationals and at least 64 Americans, the board wrote in its update.Later in the day, a State Department spokesperson said that U.S. officials and the Trump administration were "aware of approximately 90 Americans who may be impacted by the floods" in the region and that at least one more American had been rescued."We can confirm that three American citizens have been safely rescued in Nepal. We are not aware of any U.S. citizen deaths at this time," the spokesperson said, adding that the administration "has no higher priority than the safety and security of Americans."Additionally, the State Department deployed a disaster response adviser to the region to support response efforts. The department will also provide $500,000 in assistance through its global award with Catholic Relief Services, supporting emergency shelter, relief items, and water, sanitation, and hygiene assistance to flood-affected communities in Nepal, the spokesperson said."The United States extends its deepest condolences to the families and loved ones of those who lost their lives in the devastating flash floods," a post on X from the U.S. Embassy in Nepal reads. "Our thoughts are with all those affected by this disaster. The State Department is closely monitoring the situation and is deploying a disaster response advisor to the region to support response efforts."So far, local media have reported more than 350 deaths connected to the disaster."All efforts are underway to rescue and evacuate the injured and strained people," the board wrote in an updated news release.Who is missing in Nepal and China flood?People from 31 countries remained missing, including from India, which had the highest number of people unaccounted for after the flood, with at least 288 missing in Nepal and 200 stranded in China, its foreign ministry said.Among those missing are about 100 Chinese nationals missing in Nepal, its foreign ministry said; 55 Malaysian nationals, its embassy in Kathmandu reported; and 53 Ukrainians, Ukraine's foreign ministry said.The missing also include 33 Britons, 25 Canadians and at least 25 Australians, Nepal's tourism board wrote in its statement.Citizens of Belarus, Belgium, Germany, Finland, France, Hungary, Italy, Ireland, Israel, Japan, Kazakhstan, Latvia, Lithuania, New Zealand, the Netherlands, the Philippines, Portugal, Russia Serbia, Singapore, Spain, South Africa, South Korea, and Sweden also remained missing, the board said.Officials said they were working to confirm the nationalities of hundreds of other tourists traveling through the affected areas who remained missing, as well as their "safety status."What caused the Nepal flash flood?Scientists don't yet know exactly what triggered the Nepal flood, but they suspect a glacier collapse and suggest that climate change also played a role.Horrifying surveillance videos circulating online show people fleeing before a deluge crashes down on them. Drone footage also shows flooding devastation along the river as mud and floodwaters engulf riverside communities.Americans in Nepal who need "urgent assistance" related to the flooding should contact the U.S. Embassy at KathmanduACS@state.gov, the State Department said. Americans in the affected areas were also asked to follow instructions provided by local authorities as well as enroll in the department’s emergency updates program.U.S. citizens seeking information about family members in Nepal were being asked to call 1-888-407-4747 toll-free from the United States and Canada, or 1-202-501-4444 from other locations.This is a developing story.Contributing: Francesca Chambers, USA TODAY, and Gopal Sharma, Sahana Bajracharya, Navesh Chitrakar, Shilpa Jamkhandikar and Kanjyik Ghosh with ReutersNatalie Neysa Alund is a senior reporter for USA TODAY. Reach her at nalund@usatoday.com and follow her on X @nataliealund.