Rescue workers and volunteers have found 192 survivors since the iron-ore mine's tailings dam collapsed on Friday, releasing a sea of toxic waste that buried everything in its path under meters of mud.

Most of the victims are employees of mining giant Vale, which owned the dam. About 100 workers were having lunch at the company's cafeteria located just below the dam when it burst. Rescue efforts have yet to locate the building, which may have been swept away by the mudslide, according to experts.

The dam held at least 13 million cubic meters of industrial waste that is estimated to have spread over an area of 125 hectares.

The incident marks the second tailings dam collapse in three years at a Vale-owned mining operation in Brazil, flooding communities and fields with toxic sludge.

In November 2015, a tailings dam partly-owned by Vale ruptured in Mariana, also in Minas Gerais, destroying an entire community and killing 19 people. It was considered Brazil's worst environmental disaster.

Founded in Brazil in 1942 and privatized in 1998, Vale became the world's largest iron ore producer in 2013.

In total, Vale accounts for 70 to 80 percent of Brazil's iron exports, which reached $20.2 billion in 2018, and ranks as the world's second-largest exporter of the mineral.

The Brumadinho mine produces 8.5 million tons of iron ore a year, or 2 percent of the company's total annual output.

Industry observers said the company's success is partly due to the fact it pursued contracts "aggressively," but Brazil's competitive prices and the quality of the mineral were also factors.

Officials have put a freeze on Vale accounts to the tune of 11 billion reals ($2.9 billion) to guarantee funds for indemnification.

But critics are skeptical, saying Vale has yet to be held accountable for the 2015 dam disaster.