A ceremony has been held to remember victims of the mining dam collapse exactly a week after the disaster in the Brazilian state of Minas Gerais.

Dozens of people turned up to pay homage to the 110 people killed and 238 who are missing.

The ceremony was held at the site of the disaster at around 1pm local time, the hour at which the dam breached a week ago, unleashing a destructive torrent of reddish-brown mining waste.

Diggers stopped work and rescue teams all looked to the sky as 10 fire department and police helicopters released flower petals on the iron ore mining complex.

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

“It is totally devastated, it looks like there has been a war,” said 23-year-old Edvan Cristi, who lost friends who worked at the mine.

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 had been found alive since Saturday.

Brazil Dam CollapseA helicopter releases flower petals on top of an iron ore mining complex, paying homage to victims of the disaster (Andre Penner/AP)

On Friday, operations seemed to enter a new phase as firefighters began excavating the mud with heavy machinery. So far, efforts have been focused on finding bodies closer to the surface and did not involve backhoes.

The mud, which contains toxic levels of iron oxide, plastered 252 hectares of the adjacent city of Brumadinho and the Paraopeba River.

Vale SA, the company that ran and operated the dam, said the residues did not have dangerous levels of metals but experts argue that the impact on the environment 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 directly from the Paraopeba or 109 yards around it.

Brazil Dam CollapseThe Paraopeba River in Brumadinho has been heavily contaminated (Andre Penner/AP)

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

Hundreds of municipalities and larger cities such as Petrolina, 870 miles from Brumadinho, get drinking water from the Sao Francisco River.

The wave of mud is currently moving toward the Sao Francisco very slowly but officials hope the Retiro Baixo hydroelectric dam and plant complex about 185 miles from Brumadinho will prevent the mud from contaminating it.

The mud is expected to reach the Retiro Baixo dam between February 5-10.