More than 500 foreign tourists are missing after deadly floods hit the Nepal-Tibet border on Wednesday.

The flooding began on the morning of August 26, when a surge of water, mud, and debris entered Nepal from the autonomous Chinese region of Tibet via the Bhote Koshi River, Nepal's Tourism Board said.

More than 350 people have died, and more than 1,300 are missing, local authorities said earlier on Thursday, though exact numbers are unclear.

The Tourism Board's latest update listed 667 missing travelers in Nepal. Of those, 540 are foreign nationals, and 127 are Nepali.

The list includes 65 Americans and 25 Canadians, as well as travelers from the UK, Australia, Malaysia, and Ukraine. 178 of the missing tourists are from neighboring India, authorities said.

In total, people from more than 30 countries are missing.

The US State Department said in a press release that it was deploying a disaster response adviser and providing $500,000 through Catholic Relief Services for shelter, supplies, clean water, and sanitation. It also said the US Embassy in the capital Kathmandu is working with local authorities to locate and assist Americans.

Global Affairs Canada said it was aware that Canadians had been affected and was ready to provide consular assistance. It said power outages were making communications difficult.

The floods hit communities along the Bhote Koshi and Trishuli rivers, north of Kathmandu.

The US Geological Survey initially recorded a magnitude 4.4 earthquake about 40 miles north of the capital. It later updated its event page to say that no earthquake occurred and that the signal came from a glacier collapse and debris flow that released energy equivalent to a magnitude 5.2 earthquake.

What triggered the glacier collapse is still being investigated.

CCTV footage shared online showed walls of water, mud, and debris hitting Gyirong port, the border crossing between the two countries, while other footage showed widespread damage in nearby towns.