Sitting at home, Shekhar Agrawal dials number after number, hoping one of them might offer clues to the whereabouts of his sister and teenage niece – American tourists who have been missing since catastrophic flash flooding devastated Nepal and Tibet on Wednesday.

“This is the crucial golden hour,” he told CNN on Thursday from the Indian financial hub of Mumbai. He flipped through several photos of his sister, 54-year-old Rekha Shashidharan, and her daughter, 14-year-old Rashi Shashidharan, both from New York.

The next two to three days will be critical for “quick action” to find those injured or missing, he said, urging authorities to share information promptly with families.

The mother and daughter are among 90 Americans missing after the devastating landslide and flood, which tore through steep mountain gorges near the Nepal-China border and surged downstream along a river, wiping out entire villages.

President Donald Trump said the US is willing to send “any help” to Nepal, calling it a “terrible” disaster, as countries around the world send aid, relief supplies and assistance.