KATHMANDU, Nepal (AP) — Authorities were intensifying rescue efforts after catastrophic flooding in Nepal and Tibet killed at least 900 people and left more than 4,700 missing.

“We are working in search and rescue of the stranded people from hills, settlements and river areas,” said Brig. Gen. Raja Ram Basnet, Nepal’s army spokesman.

Multiple foreign teams were also assisting local rescuers to find trapped workers in hydropower tunnels. Officials say at least 90 people are trapped in multiple tunnels of hydropower plants.

Nepal’s disaster agency said Monday that 903 deaths had been counted in that country, with 4,247 people, including 592 foreigners, missing. As of Sunday, Chinese authorities reported 16 deaths and 546 missing, and Chinese state media said 261 of the missing were foreigners, including over a hundred Nepalis.

Wednesday’s flash floods started after a glacial collapse high in the Himalayan region. Scientists who studied satellite images said bedrock underneath a glacier high in the Himalayan region had collapsed, taking part of the glacier with it. The rockfall was so extreme that it registered as a magnitude 5.2 seismic event.

The rocks and melted water then swelled the rivers in the valleys below, causing a torrent of water that swept buildings, bridges and earth downstream in Tibet and Nepal.

Authorities in Nepal warned of possible fresh flooding and urged residents in flood-affected districts to remain on high alert after water levels rose in the Bhotekoshi River.

The latest warnings came after Chinese authorities informed their Nepalese counterparts of increased water flow upstream, according to Dharam Raj Uprety, chief executive of Nepal’s National Disaster Risk Reduction and Management Authority.

The Chinese state news agency Xinhua, citing the country’s water resources ministry, said a new lake formed after Wednesday’s floods high in the mountains had largely drained.

But Xinhua said the ministry warned that a crater located 5.6 kilometers (3.5 miles) upstream, which held an estimated 1.4 million cubic meters (370 million gallons) of water, still posed some risk and required close monitoring.

The missing include hundreds of people from over a dozen countries who were in the region to work, visit the mountains or make a pilgrimage to a sacred peak. On Sunday, Chinese state media said 261 foreigners were missing in Tibet, including over a hundred Nepalis and others from around the world.

In Dhading, one of the worst-hit regions in Nepal, some residents began returning to ruined homes to see what can be salvaged.

Residents sat in homes with walls washed away by the floods, shoveling sludge-like mud and rubble off balconies or window frames. Others scanned the ground for items they could pick out of the mud and rinse off. One man had returned for his chickens, which he found alive. He tied them up and put them in the cabin of his truck.

“Everything is finished. Nothing is left. Not even our home,” Sharmila Tamang, a Dhading resident who was trying to salvage items from her home, told The Associated Press.

At a key power plant that was severely damaged by the floods, workers started inspecting the facilities Sunday to survey the destruction. The plant serves over 20,000 people across four districts.

In the town of Galchhi, a group of residents sought higher ground on a nearby bridge and watched as the river roared by. Some pointed to enormous rocks washed downriver during the earlier floods, while others standing on a suspension bridge were warned off with whistles.

Along the river, homes, vehicles and farm tractors could be seen jutting from the thick gray-brown sediment that enveloped entire villages in some areas. Parts of rice terraces along the riverside had dropped into the river after landslides hit them.

Homes and businesses left intact after the flooding were still without electricity on Sunday, as twisted power line poles and wires lay tangled in the mud.

Residents of flood-hit villages said they were struggling to make sense of near-constant alarms they've received since the initial floods.

“Sometimes they say a flood is coming, then we have to run again to higher ground, even at night. There is also rain,” said Govind Shreshta, a resident. “It’s really difficult for me. I have a 72-year-old father and 70-year-old mom. I must carry them and I am exhausted. It’s going on like this for those who are still alive.”

Large concrete and smaller suspension bridges were destroyed, leaving communities on the other side of the river with less easy access.

“Those who are there are now stuck there. Those who are here are stuck here. It’s going to be very difficult,” said Sattan Singh Tamang, 47, who was working near a bridge when Wednesday’s floods came.