Massive landslides and flash floods on the Nepal-Tibet border have caused widespread damage and left hundreds dead or missing.

Search and rescue operations are under way. Chinese state media has said there are significant casualties, while Nepalese officials anticipate “huge scale loss”.

Here is what we know so far.

Nepal’s foreign minister earlier said an earthquake was reported on the Tibet-Nepal border shortly before the landslide, suggesting it may have triggered the disaster.

But the United States Geological Survey’s latest analysis suggests there was no earthquake, raising questions about what caused the landslide itself.

One possibility is that water from rainfall or melting ice may have destabilised the ground or ice, triggering a chain reaction.

Climate change is known to be driving faster glacier melt in the Hindu Kush Himalaya region, but scientists say it is too soon to pinpoint its role in this specific event.

Scientists are now trying to piece together the order of events.

They’ll be looking at satellite images of exactly where the landslide occurred, whether any glacial lakes suddenly drained, and where the river might have become blocked, as well as data on recent rainfall.

A deluge of material careered towards northern Nepalese towns, including areas popular with mountaineering tourists and pilgrims. The border is around 40 miles (64.4km) north of Nepal’s capital city Kathmandu.

Footage showed a wall of mud and rock sweeping away buildings, roads and vehicles, as people fled the fast-moving wave of material in the Nuwakot region.

In one video, a towering wall of water and mud was seen rushing down a gorge along the Trishuli River and enveloping the Rasuvagadhi Border check point, a multi-storey building.

Severe flooding has been reported along the Bhote Koshi, Trishuli and Narayani rivers.

Deaths have also been reported in villages on the Tibetan side of the border.

The number of people killed or missing is still becoming clear.

Nepali police say at least 162 people have died. Among those killed, 64 were found in downstream areas in the Chitwan district while another 26 were found in Nawalparasi East.

The number of people missing in the mudslide disaster in Tibet’s Gyirong county has risen to 558, China’s state broadcaster CCTV said on Thursday.

Among these are 260 foreign nationals, CCTV said, adding that the death toll remained at three.

The border at Gyirong is the main crossing point for tourists and traffic between China and Nepal.

Nepal had earlier also said that some 579 tourists were missing, with 466 foreigners among them. It is not clear if any of the missing in the Nepali and Chinese figures have been counted twice.

Nepal’s prime minister said “the entire nation has been left shocked and deeply distressed” and that officials would coordinate with China on the response.

China’s President Xi Jinping urged an “all-out” search effort, and promised stronger monitoring and early warning systems to prevent secondary impacts.

In neighbouring India, Prime Minister Narendra Modi said his government was “prepared to provide Nepal with all possible types of humanitarian assistance”.

UN Secretary General António Guterres says he is “saddened by the severe flooding”, adding that UN teams and partners are mobilising supplies and personnel in Nepal to support the government-led response.

The US has promised $500,000 in aid which will be used to cover emergency shelter, water, sanitation and other relief items for communities affected by the floods.

UK Prime Minister Andy Burnham said the British government would do “everything we can” to support British nationals in Nepal.

Tourists from all over the world come to Nepal for its mountains and sacred sites. Official figures suggested at least 291 foreigners are among the missing, including:

Smaller numbers of travellers from South Korea, South Africa, Portugal and the Netherlands are also among the missing.