Families of those missing after Nepal floods struggle to cling to hope

Kathmandu, Nepal — Five days after a rocky mountainside and the glacier it supported collapsed near Nepal's border with Tibet, unleashing torrents of flash floodwater , mud and debris on the valleys below that swept away everything in their path, rescuers were still searching Monday for reasons to hope.

Over the weekend, a 6-year-old girl was miraculously pulled from the mud-covered rubble, fueling hope that more of the 4,200 people still listed as missing in the wake of the disaster could be found alive.

Nepal's national disaster agency said Monday that at least 903 people had been killed, and the fear is that the toll will spiral as recovery efforts continue along the scars carved into the landscape by the raging floods.

But the danger hasn't passed. The sacred Trishuli River was surging again Monday , this time from heavy monsoon rains that have spurred search and rescue teams to try and move even faster to find anyone still alive in the ruins.

Samarth Srivastav was among the thousands of people desperately hoping a loved one might still emerge from the layers of thick mud and rubble in the Himalayan valleys.

"We're just trying to hope for good news now," Samarth told CBS News from Atlanta.

His father Vivek was on the Nepal-Tibet border when the disaster struck last week.

Samarth said his father joked with him on their last phone call about how steep the river valley walls around him were, saying, "You know, if I fall down there, like, I'll get swept away."

Just hours after the call, a tsunami of glacial ice, water and mud swept away Tibet's immigration checkpoint on the border, and Vivek hasn't been heard from since.

"Initially after hearing about it, you know, it was kind of like, okay, you know, maybe by the end of the day, you know? Might hear something back. And then the next day came and we didn't hear anything all day. And then more and more," he said. "As the number of missing people on record started to increase and, like, the severity of the situation actually started to hit, you know — we're seeing all these videos pop up on social media of people recording the disaster and everything that actually happened — I think that's when we actually started to get worried and realize that something might actually be wrong. This is actually a really bad situation."

Since then, Samarth said it has been nothing but "increasing anxiety" for his family.

"We still have the hope that he's probably okay — he's able to come back, he's probably doing fine out there," he said. "But, it's the fact we don't know anything yet, is just so scary to us."

The torrents of floodwater and everything they picked up and carried with them pushed as far as 150 miles away, into neighboring India.

At Nepal's biggest hospital, in the capital Kathmandu, an outside wall has been all but covered in posters bearing the photos of bodies recovered from the calamity. Another wall, on a smaller street nearby, was starting to fill up Monday.