Details at this time are unclear as to what exactly caused an enormous glacier collapse on the Andean mountain of Salkantay in Peru. Satellite images should solve the mystery of how the collapse started.

There was a similar example of  glacial collapse ice in 2016 in the Himalayas of Tibet but, it involved the collapse of two separate glaciers.

( O/T At the Chinese border with Tibet in the Himalayas, thousands of unknown pathogens were recently discovered. ) 

The collapse at the foot of Machu Picchu was first reported by Diario Correo. The town of Santa Theresa was effected by the mudflow.

The AGU blog writes:

On 23 February 2020 (corrected – this was erroneously reported as 24 February 2020) an enormous, catastrophic debris flow tore down the Salkantay River in Santa Teresa, Peru.  This event has killed at least four people, with a further 13 reported to be missing.  Given the magnitude of the flow, this number is probably uncertain.

A mudflow on this scale usually requires an extraordinary cause.  Diario Correo in Peru has an explanation – this event was caused by glacial collapse on Salkantay mountain.  This hypothesis is proposed by Oscar Vilca Gómez, who the article describes as a specialist in Hydrology and Glaciology.  He visited the site site of the detachment as part of a research team from the National Institute for Glacier Research of the Ministry of Environment.  They propose that an ice / rock avalanche detached from the mountain, crossed the Salkantay Cocha lake, and generated the huge debris flow.

Video of the glacial outburst flood.