A week after the deadly collapse of a mining dam in the Brazilian state of Minas Gerais a shocking video has emerged of the instant a wall of mud and water claimed the lives of 110 known victims and buried some 238 whose bodies have yet to be found.

A memorial ceremony was held at the site of the disaster around 1pm on Friday (local time), the hour at which the dam collapsed on January 25, unleashing a destructive torrent of reddish-brown mining waste.

Backhoes stopped digging in the mud as 10 fire department and police helicopters released flower petals on the iron ore mining complex.

A priest also said a brief Mass in front of a tall pink cross that had been planted in the mud.

Local resident Edvan Cristi, 23, lost several friends who worked for the mining company and said his town would suffer tremendously, as the ledger of the dead and missing represented a huge slice of the younger generation.

“Everybody, the majority, worked in mining,” he said.

A spokesman for the Minas Gerais Fire Department said after the ceremony that authorities were not calling off the search for bodies, although no one has been found alive since the hours immediately after the lethal tide engulfed all before it.

Now is a vast toll in human life the only casualty. The tailings, which contain toxic levels of iron oxide, plastered 252 hectares between the Brumadinho and the Paraopeba rivers and contaminated local rivers.

Vale SA, the mine operator, insisted the residues did not contain dangerous levels of metals, but environmental experts argue the impact could be irreversible.

Authorities and environmental organisations have begun testing water quality around the mining complex, while state and federal authorities have told residents to refrain from using water from the Paraopeba.

The Paraopeba flows into the much larger Sao Francisco River, which could also be contaminated.

Hundreds of municipalities and larger cities such as Petrolina draw their drinking water from the Sao Francisco.

-with AAP