The flood was caused by the failure of a dam, releasing water from the Vega de Tera reservoir.

The collapse released 7.8 million cubic metres (280×10^6 cu ft) of water from the Vega de Tera reservoir.

At an initial peak discharge of 13,000 cubic metres per second (460,000 cu ft/s), the flood traveled 8 kilometres (5.0 mi) downstream towards Ribadelago.

The time between hearing a loud roar as a result of the break and the subsequent torrent of water was insufficient for residents to escape.

[2] Many of the buildings were destroyed by the rapid flood, which and an estimated maximum flow depth of 34 metres (112 ft).

[1] The disaster led to the creation of Instruction for the Project, Construction and Exploitation of Large Dams by the Ministry of Public Works in 1962.

[4][5] In December 1959, seven workers from Hidroeléctrica Moncabril, and three from the company that constructed the dam were indicted by the Court of Valladolid.

According to an eyewitness present during the construction of the dam, leaks occurred, which had to be controlled by measuring water in the reservoir.

The court of justice sentenced the then managing director of the company, two engineers and an expert as directly responsible for the works to one year in prison for the crime of reckless negligence.