A massive flash flood swept away villages near the Nepal-China border on Wednesday, killing many and prompting a helicopter rescue operation, while Tibet reported major casualties from a related mudslide.

At least 160 people were killed in Nepal and hundreds more, most of them foreigners, were listed as missing on Wednesday in both Nepal and Tibet after flash flooding tore through border areas, according to authorities. The flooding was determined to have been caused by the collapse of a glacier, U.S. officials later said.

A flash flood warning was issued by the National Weather Service in Flagstaff at 12:07 p.m. on Aug. 30. This warning applies to Coconino County.

ABC News meteorologist Leslie Lopez is tracking the flash-flood threat for parts of the West and the dangerous heat for millions of Americans.

Fox News correspondent Stephanie Bennett reports as rescuers in Nepal battle rain and mud while searching for thousands missing after catastrophic flash floods on ‘Fox Report.’

A severe thunderstorm warning was issued by the National Weather Service in Flagstaff at 2:28 p.m. on Saturday, Aug. 29.

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