A Texas couple were celebrating their 25th wedding anniversary on a religious pilgrimage to Nepal when a glacier collapsed and caused devastating floods that have now claimed the lives of over 1,000 people.

Archana Suresh, 46, and Raghu Rajan, 50, of Murphy, Texas, set off on a religious pilgrimage to Mount Kailash to mark the milestone and were expected to cross the hard-hit Nepal-China border last Wednesday morning.

'They were extremely excited about this trip,' Rajan's sister-in-law Divya Chandrashekar told CBS News. 'They [kept] talking about it all the time.' 

But when the devastating floods hit at around 8.30am on August 26, the couple were near the Friendship Bridge that connects Nepal to China. The bridge was then completely wiped out in the storms.

Their family has been left in the dark about their whereabouts ever since, as the couple's two college-aged children pray that they made it out safely.

'We're keeping our fingers crossed that they had enough time to get to a higher ground or something,' Chandrashekar said.

'We're just hoping a miracle happens and all of them show up safe and sound.'

The couple are just two of nearly 85 Americans who remain unaccounted for following the deadly flash floods. 

The devastating sequence of events began last Wednesday morning, when the earth started shaking along the Nepal-China border.

The US Geological Survey initially detected the shaking as a magnitude 5.2 earthquake but later determined that a massive section of glacier had collapsed.

The United States Geological Survey described the seismic event as an extremely powerful 'glacial collapse and debris flow' that caused catastrophic impacts downstream.

As the ice mass plummeted, it was pulverized into a fast-flowing mix of freezing water, debris and rocks that swept down the mountainside into the Lende Khola River, razing villages along the way.

More than 1,000 deaths have since been reported on the Nepal side of the border alone, as nearly 4,000 people remain missing – including 583 foreign nationals, the country's disaster agency reported on Tuesday. 

Chinese officials have also reported 16 deaths and 546 missing, including 261 foreigners. 

But rescue efforts in both countries have been hindered by the massive damage from the flood, as landslides, destroyed roads and widespread damage left some remote areas completely cut off.

Crews have also faced challenging conditions as they searched unstable terrain and piles of debris, raising fears the death toll could rise as rescuers reach isolated communities. 

Rescuers are now trudging through those treacherous conditions to reach hundreds of workers believed to be trapped inside tunnels at hydropower projects in Nepal damaged by the floods. 

About 900 workers are missing from a dozen projects, with roughly 500 believed to be trapped in tunnels, according to local authorities.

Meanwhile, in China, rescue crews scoured areas hit by mudslides, particularly around the Gyirong Port border crossing, which was left decimated.

Some rescuers, aided by search dogs, searched gaps among rocks and debris for signs of life. Other teams used heavy machinery to clear a major highway leading to Gyirong Port, hoping to clear the way for equipment, personnel and supplies to reach the disaster zone, according to China's state-run Global Times newspaper. 

At the same time, police in Kathmandu worked in heavy rain on Tuesday to bury dozens of bodies in multiple trenches next to a forested area.

Barbed wire was erected around the site, while blue numbered markers identified the graves of people whose names were not yet known.

Authorities in Nepal have been burying bodies in temporary graves until they can be identified. They are preserving DNA samples, photographing distinguishing facial features and recording other identifying details.

Each body is assigned a reference number to help families identify and claim the remains later. 

Still, at least 11,814 people have been rescued after emergency crews in Nepal used helicopters and other aircraft to reach stranded communities, authorities said.

Efforts are now also being stepped up to provide assistance to survivors in areas where roads and other transportation routes had been damaged or cut off.

China's Foreign Ministry spokesperson, Guo Jiakun, said a second batch of relief supplies was being sent to Nepal, including drones, DNA testing and water purification equipment. 

Chinese DNA testing experts will also help Nepal identify bodies, he said.